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Animal trypanosomosis is a significant livestock disease with economic and social repercussions, reducing the supply of animal products and restricting the utilization of animals for traction and transportation. In Ethiopia, it is prevalent and poses a major hindrance to the advancement of animal production. This repeated cross-sectional study was aimed at assessing seasonal variation in bovine trypanosomosis prevalence and tsetse fly density and identifying the potential risk factors in the Loka Abaya and Derara districts of the Sidama National Regional State. Blood samples were collected from 964 cattle, 484 samples during the dry season, and 480 during the wet season. The buffy coat method was employed to analyze these samples. Furthermore, 78 standard NGU traps were set up at various locations in the two districts during both seasons for entomological investigation. The overall apparent prevalence of trypanosomosis was 9% (95% CI 7.3-11.0), without a significant difference (p > 0.05) between the dry season (7.4%) and wet season (10.6%). The apparent prevalence was significantly higher in Loka Abaya (11.8%) than in Derara (6.3%) district (OR = 2.04; p = 0.003) and in cattle with black coat color (29%) than in mixed color (6.8%) (OR = 5.3; p < 0.001). The majority of infections were caused by Trypanosoma congolense (70%), followed by T. vivax (29%), and mixed infections (1%) with the two species. The average packed cell volume (PCV) was significantly (p < 0.0001) lower in infected animals (20.7 ± 4%) compared to uninfected ones (25.5 ± 5.4%), in cattle examined during the dry season (24.1 ± 6%) versus the wet season (26.1 ± 4.7%), in cattle sampled from the Loka Abaya district (24.2 ± 5.5%) versus Derara district (26 ± 5.3%), and in cattle with poor body condition (23.6 ± 5.7%) compared to those with good body condition (26.5 ± 5.3%). A total of 5282 flies were captured during the study, with 4437 (84%) being tsetse flies (Glossina pallidipes), 439 (8.3%) Tabanids, 190 (3.6%) Stomoxys spp., and 216 (4.1%) Musca spp. The apparent density (AD) of G. pallidipes was 28.4 flies/trap/day, showing no statistically significant difference between wet (32.1) and dry (24.6) seasons (p > 0.05). The AD of G. pallidipes was significantly (p < 0.001) higher in the Loka Abaya district (57.3) than in the Derara district (0.9). The study highlights a moderate trypanosomosis apparent prevalence and high AD of G. pallidipes, showing significant variation between the study districts but no seasonal difference. The observed apparent prevalence of trypanosomosis and tsetse fly density notably affects animal health and productivity. As a result, strategies for vector control like insecticide-treated targets, trypanocidal medications for infected animals, and community-based initiatives such as education and participation in control programs are recommended., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Bovine trypanosomosis transmitted by tsetse flies is a major constraint to cattle health and productivity in all sub-Saharan countries, including Uganda. The objectives of this study were to determine the prevalence of bovine trypanosomosis and identify its associated risk factors and the species of trypanosomes associated with the disease., Methodology: A cross-sectional study was conducted around Murchison Falls National Park, Uganda from January 2020 to April 2020. Trypanosomes were detected in blood samples by PCR analysis targeting the internal transcribed spacer 1 (ITS-PCR assays), and trypanosomes in positive blood samples were sequenced., Results: Of 460 blood samples collected and tested, 136 (29.6%) were positive for trypanosome infections and 324 (70.4%) were negative. The overall trypanosome prevalence was 29.6% (95% confidence interval 25.4-33.8%), attributed to three trypanosome species. Of these three species, Trypanosoma vivax was the most prevalent (n = 130, 28.3%) while the others were detected as mixed infections: T. vivax + Trypanosoma congolense (n = 2, 0.4%) and T. vivax + Trypanosoma evansi (n = 1, 0.2%). There were significant differences in trypanosome prevalence according to sex (χ 2  = 62, df = 1, P < 0.05), age (χ 2  = 6.28, df = 2, P = 0.0043) and cattle breed (χ 2  = 10.61, df = 1, P = 0.001)., Conclusions: Trypanosomosis remains a major limitation to cattle production around Murchison Falls National Park and interventions are urgently needed. In our study, the prevalence of trypanosome infections was high, with T. vivax identified as the most prevalent species. Age, sex and breed of cattle were risk factors for trypanosome infection., (© 2021. The Author(s).)

Despite some researchers reporting clinical signs in cattle associated with Trypanosoma theileri, its role as a pathogen is still unclear. We describe here the isolation of Trypanosoma theileri during a routine laboratory investigation. Mature and immature vital parasitic forms were observed within hematopoietic cell cultures from the bone marrow of one cow for monocyte isolation. The animal was submitted to clinical examination and blood sample counting (CBC). Postmortem analysis included gross and histological examination and PCR in the liver, spleen, brain, lymph nodes, and lungs. PCR and Giemsa staining were used for parasite identification. A second cow belonging to the same farm was positive for Trypanosoma theileri by PCR performed on blood sample. In this case, the postmortem analysis included also testis. Clinical examination showed only a reduction in body weight in both cases. The CBC revealed an increase of lymphocytes and neutrophils while red blood cells were within the normal range. Spleen was slightly increased in volume and the histology revealed a proliferative activity of the white and red pulp. The biomolecular analysis identified the parasite as Trypanosoma theileri and its DNA was detected in the bone marrow, testis, and brain. The unusual finding of parasite in the brain, testis, and bone marrow raises new clinical implication on disease course and also possible sexual transmission.

A cross-sectional study was carried out on 594 bovines (341 buffalo adults, 31 buffalo calves, 163 cattle adults, and 59 cattle calves) to assess the exposure of native bovine population to T. evansi elicited trypanosomiasis in the low-lying areas of Punjab (India). We ruled out the endemicity of the disease with 10.77% (95%CI = 8.53-13.52) sero-positive and 23.56% (95%CI = 20.33-27.15) suspected cases by card agglutination assay. We have presented the spatial distribution of these cases as a guideline to local veterinary practitioners and policy-makers. The categorical assessment of risk factors revealed buffalo adults are the most susceptible group in the state despite insignificant differences in farm management practices. A significant increase in the WBC, platelet, AST and serum iron, and decrease in haemoglobin, haematocrit volume, and serum glucose was recorded in both T. evansi positive and suspected animals., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Bovine trypanosomosis is a problem in the livestock industry in Nigeria. A longitudinal survey of cattle sampled during the wet and dry seasons was conducted from April 2016 to March 2017. Blood samples were collected by random sampling from 745 cattle in southwest Nigeria and screened for trypanosomes by internal transcribed spacer-polymerase chain reaction (ITS-PCR). Cattle positive for Trypanozoon DNA were further screened with the Rode Trypanozoon antigen type (RoTat) 1.2 PCR and Trypanosoma brucei gambiense glycoprotein (TgsGP) genes for T. evansi and T. b. gambiense respectively. Trypanosome DNA was amplified in 23.8% (95%CI: 20.8-26.9) of cattle with significantly higher prevalence in wet season (95%CI: 22.9-30.8) when compared to the dry season (95%CI: 14.3-23.6). A high prevalence was observed in Fulani cattle farms 54.1% (95%CI: 42.78-64.93%) while the prevalence was lower in institutional farms 14.7% (95%CI: 10.10-20.97%). Trypanosoma vivax was the most prevalent trypanosome observed (11.54% (95%CI: 9.44-14.04%)), followed by T. congolense 8.5% (95%CI: 6.67-10.67%) T. b. brucei 4.8% (95%CI: 3.51-6.62%) and T. evansi 1.74% (95%CI: 1.02-2.96%). Mixed infections were observed in 2.8% (95%CI: 1.85-4.27%) of cattle. Seasonal variation revealed a predominance of T. congolense and T. vivax in wet and dry season, respectively. The high prevalence of Trypanosoma species in cattle indicates a need for expanded surveillance for AAT in southwest Nigeria. Migration, settlement patterns, increased marketing and management types were some of the risk factors identified for AAT., (Copyright © 2018 Elsevier B.V. All rights reserved.)

African animal trypanosomosis (AAT) is a parasitic disease considered to be one of the greatest constraints to cattle production in Tanzania. There is insufficient information on seasonal occurrence of AAT and management practices in Monduli District of the Maasai Steppe ecosystem to guide and prioritize AAT control programs. A cross-sectional survey was undertaken in 10 randomly selected villages of Monduli District. Information on seasonal animal movements, including wildlife interaction, and AAT management practices was gathered using a standardized questionnaire with 130 pastoralists. Blood samples were collected from a total of 960 cattle, in wet and dry seasons. An entomological survey was also undertaken in the dry season. Polymerase chain reaction targeting the internal transcribed spacer 1 (ITS1) was used for parasite identification in cattle blood and in tsetse flies. The overall apparent prevalence of AAT in cattle was 5.8% (95% CI of 4.1-8.3) and 4.2% (95% CI of 2.7-6.3) during wet and dry reasons, respectively. Trypanosoma vivax was the most common species identified in cattle. All tsetse flies (n = 426) collected were trapped in Esilalei village which is in close proximity to Lake Manyara National Park. Tsetse fly infection status was determined to be 7.0%; (CI 95% of 4.9-9.8%) with nearly 50% of infections due to T. congolense. All 130 cattle owners reported that they could easily recognize AAT and the majority (75%) identified the most prominent clinical signs. Nearly all owners (98.5%) identified that tsetse flies were responsible for AAT transmission. All cattle owners (100%) reported the use of trypanocides for AAT treatment, while 2.3% reported to also use herbal medicine. The trypanocides, Novidium® and Berenil®, were the most frequently reported commercial drugs and were used by 42% of cattle owners. Vector control by hand spraying was reported by the majority (90.8%) of cattle owners, while dipping and deployment of insecticide-impregnated targets were reported by few cattle owners (16.2% and 5.4%, respectively). The majority of cattle owners (83.1%) reported to move cattle away from home villages during the dry season with many migrating to areas in close proximity to wildlife parks. This study confirms the presence of circulating pathogenic trypanosomes in tsetse flies which continue to pose a threat to Maasai cattle. The seasonal movement of cattle during the dry season was associated with more clinical cases of cattle trypanosomosis. This study demonstrates the need to strengthen surveillance and control strategies for AAT., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Animal trypanosomosis is one of the major disease problems affecting agricultural productivity in Ethiopia. The impact of the disease is believed to vary with season and agro-ecologies in line with fly vector distribution. A cross-sectional study on bovine trypanosomosis was conducted from November 2015 to June 2016, in seven selected villages of Gidami district, Oromia Regional State, western Ethiopia. A total of 930 blood samples were collected and subjected to parasitological and hematological analysis., Result: The overall prevalence of bovine trypanosomosis was 14.1%. The seasonal prevalence shows 9.06% in early dry and 18.4% in early rainy seasons. Three trypanosome species, Trypanosoma congolense, Trypanosoma vivax and Trypanosoma brucei were identified in the examined animals. T. congolense followed by T. vivax were the predominant species (respectively 59.0 and 35.9% in early dry season and 62.0 and 22.8% in early rainy season). The prevalence of T. vivax remained similar in both early dry and early rainy seasons in both lowland and midland agroecologies whereas T. congolense was more dominant in the lowland area in both seasons compared to mid land study sites. The disease was more prevalent in lowland (23.9%) compared to midland (11.1%) during early rainy season (P < 0.001) whereas no significant difference was observed between the two agroecologies during early dry season (P = 0.165). Packed cell volume (PCV) was much lower in parasitemic animals than in aparasitemic cattle whereas the mean PCV value for parasitemic animals (20.36%; 95% CI 19.56 to 21.16) in early dry season was similar to values in early rainy season (20.46%, 95% CI 18.84 to 21.08%). A similar situation was noticed for animals in both low land and mid land study sites., Conclusion: Overall, the detection of trypanosomes in blood was significantly affected by agro-ecology, season and body condition of the animals. Special emphasis should be given to integrated trypanosomosis management in early rainy months where fly population is believed to start increasing.

Background: Animal African trypanosomiasis (AAT) greatly affects livestock production in sub-Saharan Africa. In Ghana prevalence of AAT is estimated to range between 5 and 50%. Studies have reported serum biochemical aberrations and variability in cytokine profiles in animals during infection. However, information regarding the biochemical parameters and cytokine profiles associated with natural infections are limited. This study was therefore aimed at investigating changes in the levels of serum biochemical parameters and inflammatory cytokines during a natural infection., Methods: Nested internal transcribed spacer (ITS)-based PCR and sequencing were used to characterise trypanosome infection in cattle at two areas in Ghana (Adidome and Accra) of different endemicities. The cattle were sampled at four to five-week intervals over a period of six months. Levels of serum biochemical parameters, including creatinine, cholesterol, alkaline phosphatase (ALP), alanine aminotransferase (ALT), total bilirubin and total protein and cytokines (interleukin 10, interleukin 4, interleukin 12, interferon gamma and tumor necrosis factor alpha) were measured in serum samples and then compared between infected cattle and uninfected controls., Results: The predominant trypanosome species detected in Accra (non-endemic) and Adidome (endemic) were Trypanosoma theileri and Trypanosoma vivax, respectively. Serum biochemical parameters were similar between infected and uninfected cattle in Accra. Infected cattle at Adidome however, had significantly higher levels of ALP, creatinine, total protein and total bilirubin (P < 0.05) and significantly lower levels of cholesterol (P < 0.05) at specific time points. At basal levels and during infection, significantly higher pro-inflammatory to anti-inflammatory (Th1/Th2) cytokine ratios were observed in cattle at Adidome compared to Accra (P < 0.05), indicating a shift towards Th1 immune response in Adidome. Levels of IL-10 were, however, significantly elevated in infected cattle in Accra (P < 0.05), suggesting high anti-inflammatory cytokine response in Accra., Conclusion: These results suggests that cattle in an endemic area repeatedly infected with trypanosomes of different species or different antigenic types demonstrate high pro-inflammatory (Th1) immune response and biochemical alterations whereas cattle in a non-endemic area with predominantly chronic T. theileri infections demonstrate high anti-inflammatory response and no biochemical alterations.

We compared the nested internal transcribed spacer (ITS) PCR and the 18S PCR-RFLP (restriction-fragment length polymorphism) pan-trypanosome assays in a cross-sectional survey of bovine trypanosomiasis in 358 cattle in Kwale County, Kenya. The prevalence of trypanosomiasis as determined by the nested ITS PCR was 19.6% (70/358) and by 18S PCR-RFLP was 16.8% (60/358). Of the pathogenic trypanosomes detected, the prevalence of Trypanosoma congolense and Trypanosoma vivax was greater than that of Trypanosoma simiae The nested ITS PCR detected 83 parasite events, whereas the 18S PCR-RFLP detected 64; however, overall frequencies of infections and the parasite events detected did not differ between the assays (χ(2) = 0.8, df = 1, p > 0.05 and χ(2) = 2.5, df = 1, p > 0.05, respectively). The kappa statistic (0.8) showed good agreement between the tests. The nested ITS PCR and the 18S PCR-RFLP had comparable sensitivity, although the nested ITS PCR was better at detecting mixed infections (χ(2) = 5.4, df = 1, p < 0.05)., (© 2016 The Author(s).)

In continuing efforts to better understand the genetics of bovine trypanosomosis, we assessed genetic diversity of Trypanosoma brucei and Trypanosoma evansi in naturally infected Nigerian cattle using repetitive DNA and internal transcribed spacer 1 of rDNA sequences and compared these sequences to species from other countries. The length of repetitive DNA sequences in both species ranged from 161 to 244 bp and 239 to 240 bp for T. brucei and T. evansi, respectively, while the ITS1 rDNA sequences length range from 299 to 364 bp. The mean GC content of ITS1 rDNA sequences was 33.57 %, and that of repetitive sequences were 39.9 and 31.1 % for T. brucei and T. evansi, respectively. Result from sequence alignment revealed both T. brucei and T. evansi repetitive DNA sequences to be more polymorphic than ITS1 rDNA sequences, with moderate points of deletion and insertions. T. brucei separated into two clades when subjected to phylogenetic analysis. T. evansi repetitive DNA sequences clustered tightly within the T. brucei clade while the ITS1 rDNA sequences of T. brucei were clearly separated from T. theileri and T. vivax individually used as outgroups. This study suggest that ITS1 rDNA sequences may not be suitable for phylogenetic differentiation of the Trypanozoon group and also suggest that T. evansi may be a phenotypic variant of T. brucei which may have potential implications in designing prevention and therapeutic strategies.

Background: The control of animal trypanosomosis consists, amongst other things, of the punctual treatment of new cases, primarily diagnosed by pastoralists on the basis of clinical signs. This practice suggests that many apparently healthy infected animals are left untreated. In this study animal trypanosomosis in clinically healthy zebu cattle was evaluated, the distribution of the vectors established and the epidemiological implications discussed., Methods: In 2014 two cross-sectional surveys were carried out in the Cambeef ranch. A total of 866 blood samples were collected from cattle in different sites: 549 in the dry season and 317 in the rainy season. The blood samples were subjected to parasitological examination using the buffy coat method and to PCV determination. An entomological survey on animal trypanosomosis vectors was undertaken during tsetse flies caught were identified and the mid-gut of each living non-teneral tsetse fly was examined for infections using a microscope., Results: An overall trypanosomosis prevalence of 9% was found in the cattle examined. There were significantly (P < 0.05) more trypanosome infected cattle in the dry season than the rainy season. Trypanosome-infected cattle had significantly (P < 0.05) lower Body Condition Scores (BCS) and Packed Cell Volumes (PCV) in the dry season than in the rainy season. Anemia was positively correlated with trypanosome infection. The likelihood for an animal to be parasitologically free of trypanosome infection was at least three times as high in the Gudali breed as compared with the white and red Fulani breeds. Species of trypanosomes identified were Trypanosoma vivax (73.23%), Trypanosoma congolense (15.49%) and Trypanosoma brucei (11.27%). A total of 390 tsetse flies and 103 tabanids were trapped. Two species of tsetse flies were identified: Glossina tachinoides (33.59%) and G. morsitans submorsitans (41%). Nine of the 194 non-teneral flies were infected with trypanosomes., Conclusion: Carriers of trypanosomes are present amongst apparently healthy cattle in the study site. Attempts to successfully reduce the population of reservoir trypanosomes within herds and control the disease will need to consider mass screening once every year and this should be associated with drug sensitivity tests.

Background: Fragmentation of tsetse habitat in eastern Zambia is largely due to encroachments by subsistence farmers into new areas in search of new agricultural land. The impact of habitat fragmentation on tsetse populations is not clearly understood. This study was aimed at establishing the impact of habitat fragmentation on physiological and demographic parameters of tsetse flies in order to enhance the understanding of the relationship between fragmentation and African animal trypanosomosis (AAT) risk., Methods: A longitudinal study was conducted to establish the age structure, abundance, proportion of females and trypanosome infection rate of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) in areas of varying degrees of habitat fragmentation in Eastern Zambia. Black screen fly rounds were used to sample tsetse populations monthly for 1 year. Logistic regression was used to analyse age, proportion of females and infection rate data., Results: Flies got significantly older as fragmentation increased (p < 0.004). The proportion of old flies, i.e. above ovarian category four, increased significantly (P < 0.001) from 25.9% (CI 21.4-31.1) at the least fragmented site (Lusandwa) to 74.2% (CI 56.8-86.3) at the highly fragmented site (Chisulo). In the most fragmented area (Kasamanda), tsetse flies had almost disappeared. In the highly fragmented area a significantly higher trypanosome infection rate in tsetse (P < 0.001) than in areas with lower fragmentation was observed. Consequently a comparatively high trypanosomosis incidence rate in livestock was observed there despite lower tsetse density (p < 0.001). The overall proportion of captured female flies increased significantly (P < 0.005) as fragmentation reduced. The proportion increased from 0.135 (CI 0.10-0.18) to 0.285 (CI 0.26-0.31) at the highly and least fragmented sites, respectively., Conclusions: Habitat fragmentation creates conditions to which tsetse populations respond physiologically and demographically thereby affecting tsetse-trypanosome interactions and hence influencing trypanosomosis risk. Temperature rise due to fragmentation coupled with dominance of old flies in populations increases infection rate in tsetse and hence creates high risk of trypanosomosis in fragmented areas. Possibilities of how correlations between biological characteristics of populations and the degree of fragmentation can be used to structure populations based on their well-being, using integrated GIS and remote sensing techniques are discussed.

Duplex PCR consisting of two primer sets within a single mixture for the simultaneous detection of Anaplasma marginale and Trypanosoma evansi was standardized and employed on 219 blood samples collected from cattle (165) and buffaloes (54) from eastern Punjab to evaluate the status of concurrent infection and associated risk factors. The reaction produced 257- and 407-bp amplification products targeting repetitive nucleotide sequence of T. evansi and msp1β gene of A. marginale, respectively. The nucleotide sequence analysis of individual amplicons expressed the fidelity of the primer pairs used; duplex PCR was 100% sensitive and 92.66 % specific with conventional microscopy for the detection of mixed infections. Among the agro-climatic zones of interest, undulating zone was at higher risk of T. evansi infection (odds ratio (OR) = 1.75, 95% confidence interval (CI) = 0.94-3.27), and submountain zone (OR = 1.89, 95% CI = 1.11-3.33) for A. marginale. For the concurrent infection, the relative risk among the two zones was almost unity. The cross-bred cattle population was at the highest risk of infection, may it be solo infection of T. evansi (OR = ∞, 95% CI = 1.18-∞)/A. marginale (OR = 6.39, 95% CI = 1.14-125.3) or dual infection (OR = ∞, 95% CI = 0.39-∞) of both as the indigenous cattle are resistant to the infection. Cross-bred cattle were at approximately three times the risk than buffaloes. For the dual infection, the cattle calves were at about 2.5 times higher risk than buffalo calves. Results indicate the endemic status of these infections in the region and mark out the commodities at great risk and requiring better surveillance.

Trypanosoma evansi, a haemoflagellate, causes "surra" an important chronic wasting disease of a wide range of wild and domestic herbivorous and carnivorous animals including cattle, buffaloes, camels, horses, etc. The untreated recovered animal can act as a carrier without exhibiting the disease symptoms and can be a source of infection to healthy animals. The diagnosis and subsequent treatment of the carrier animals is helpful to curb the disease. As the parasitaemia in carrier animals is very scanty, the conventional blood smear examination, which is widely practiced in the field, cannot detect such condition. For this purpose improved diagnostics are very much useful for mass sero-screening test such as ELISA. In the present study, the VSG of T. evansi was expressed in prokaryotic system (E. coli) and thereafter its immunoreactivity has been evaluated in immuno blot and enzyme immuno assay. The expressed protein showed 95.6% sensitivity, 98.0% specificity and 0.93 Cohen's kappa value, when compared with standard antigens. The developed antigen has also been validated with field serum samples from bovine, camel and horse collected from different states of India. The data showed that the developed recombinant antigen can be a diagnostic tool to detect carrier animals as well as control of the disease., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Vector-borne diseases (VBDs) continue to threaten the worldwide livestock industry, but comprehensive epidemiological surveys on such diseases have not been conducted in the Philippines. In the present study, we screened 408 bovine blood samples from 9 areas in Cebu, Philippines, for various VBD pathogens using specific PCR assays. The results revealed prevalences of 54.7, 15.4, 10.0, and 12.0% for Anaplasma spp., Babesia bigemina, Babesia bovis, and Trypanosoma (Tr.) theileri, respectively. In contrast, none of the samples were positive for Trypanosoma (Tr.) evansi, Theileria (Th.) orientalis, and Theileria (Th.) annulata. Mixed infections were observed in 24.2% of the samples tested. Phylogenetic analysis based on the 16S rRNA gene revealed that the Anaplasma spp. sequences from the present study were genetically close either to Anaplasma marginale or Anaplasma phagocytophilum. In addition, B. bovis RAP-1 and Babesia bigemina AMA-1 gene sequences were identical and monophyletic to other known B. bovis and B. bigemina sequences. On the other hand, Tr. theileri cathepsin-L like protein gene sequences shared 97.1-100% identities with those from the USA and Brazil and clustered within a single genotype in the phylogenetic tree. The molecular identification of several VBD pathogens in Cebu cattle calls for the implementation of control measures to prevent the spread of these pathogens to nearby localities or islands, and ultimately, economic losses to the Philippine economy., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The study was carried out to assess the economic burden of trypanosomosis in three villages of the Metekel zone in 2009. The disease was found to cause substantial economic losses through cattle mortality, drug purchase, and draft power loss of infected oxen. The farmers in the area were spending a significantly (p < 0.05) higher amount of money for the treatment of trypanosomosis than all other diseases combined. The overall mortality rate of cattle due to trypanosomosis was 4.4%. The mortality was significantly higher (p < 0.05) in an area where trypanosomosis prevalence was also higher. Many of the farmers prioritized losses of draft power as the most important impact of the disease. The overall prevalence of the disease was 12.1%. The disease burden was significantly (p < 0.05) higher in the rainy season than at other times of the year. In general, farmers had good knowledge on the signs and seasonality of trypanosomosis. Thus, tsetse suppression activities that involve the local community can be an important tool towards minimizing the economic burden of the disease in the area.

This study compared the prevalence of trypanosome infections estimated by PFR-loop-mediated isothermal amplification (LAMP) with conventional polymerase chain reaction (PCR) tests. One hundred forty eight cattle blood samples were collected from Robanda village, Mara region, Tanzania in April 2008. In conventional PCR, four sets of primers, specific for the detection of Trypanosoma sp., Trypanosoma brucei rhodesiense, Trypanosoma vivax, and Trypanozoon, as well as a modified LAMP were used. Conventional PCR detected no infection or up to 8, 1, and 3 infections with Trypanosoma congolense savannah, Trypanozoon, and T. vivax, respectively, whereas LAMP detected additional 44 Trypanozoon positive cases. Our results clearly indicate that the prevalence of Trypanozoon spp. in cattle in Robanda village estimated by PFR-LAMP (30.4%) was significantly higher than the estimates by PCR assays (0.6-2%). As such, future studies should target epidemiological surveys of Trypanozoon and T. brucei rhodesiense infections in possible reservoir animals by LAMP to further elucidate the actual prevalence of these parasites.

In the Mouhoun River basin, Burkina Faso, the main vectors of African animal trypanosomoses are Glossina palpalis gambiensis Vanderplank and Glossina tachinoides Westwood (Diptera: Glossinidae), both of which are riverine tsetse species. The aim of our study was to understand the impact of landscape anthropogenic changes on the seasonal dynamics of vectors and associated trypanosomosis risk. Three sites were selected on the basis of the level of disturbance of tsetse habitats and predominant tsetse species: disturbed (Boromo, for G. tachinoides) and half-disturbed (Douroula for G. tachinoides and Kadomba for G. p. gambiensis). At each of these sites, seasonal variations in the apparent densities of tsetse and mechanical vectors and tsetse infection rates were monitored over 17 months. Tsetse densities differed significantly between sites and seasons. Of 5613 captured tsetse, 1897 were dissected; 34 of these were found to be infected with trypanosomes. The most frequent infection was Trypanosoma vivax (1.4%), followed by Trypanosoma congolense (0.3%) and Trypanosoma brucei (0.05%). The mean physiological age of 703 tsetse females was investigated to better characterize the transmission risk. Despite the environmental changes, it appeared that tsetse lived long enough to transmit trypanosomes, especially in half-disturbed landscapes. A total of 3021 other biting flies from 15 species (mainly Tabanidae and Stomoxyinae) were also caught: their densities also differed significantly among sites and seasons. Their relative importance regarding trypanosome transmission is discussed; the trypanosomosis risk in cattle was similar at all sites despite very low tsetse densities (but high mechanical vector densities) in one of them.

Background: In this paper, we report an outbreak of bovine trypanosomiasis in Kurmuk District, Blue Nile State, Sudan that involved an infection with four Trypanosoma species in cattle. The outbreak occurred in June 2010 when indigenous cattle, mainly Kenana and Fulani breed types, crossed the national Sudanese border to Ethiopia and returned. A veterinarian was notified of massive deaths in the cattle populations that recently came from Ethiopia. All animals involved in the outbreak were from the nomadic Fulani group and resident local cattle were not infected and no death has been reported among them. A total of 210 blood samples were collected from the ear vein of cattle. A few samples were also collected from other domestic animals species. Parasitological examinations including hematocrit centrifugation techniques (HCT) and Giemsa-stained thin blood films were carried out. ITS1-PCR, which provides a multi-species-specific diagnosis in a single PCR, was performed., Findings: Parasitological examinations revealed that 43% (91/210) of the affected cattle population was infected with two morphologically distinct trypanosomes. Seventy animals (33.3%) were infected with T. vivax and twenty one (10%) with T. congolense. In contrast, ITS1-PCR was able to identify four Trypanosoma species namely T. vivax, T. congolense, T. simiae and T. brucei in 56.7% (80/141). T. brucei showed the highest prevalence of 36.9% (52/141) and the lowest 19% (27/141) was displayed by T. congolense. Furthermore, and because ITS1-PCR could not differentiate between T. brucei subspecies, serum resistance-associated (SRA) gene based PCR was used to detect the human T. brucei rhodesiense in T. brucei positive samples. None of the samples was shown positive for T. b. rhodesiense. The identity of the 400 bp PCR product originating from T. simiae, was further confirmed by sequencing and subsequent phylogenetic analysis., Conclusions: The outbreak of bovine trypanosomiasis occurred in the Blue Nile State was caused by mixed infection of two or more Trypanosoma species and the conventional parasitological examinations were not reliable in identifying all the species of Trypanosoma involved in the outbreak. It is difficult to determine the cause of the disease for the reason that the current enzootic situation in the resident cattle in the region is poorly understood. The study concluded that there are at least four species of trypanosomes that caused this outbreak in the Blue Nile State. The presence of mixed infections might have exacerbated the severity of the disease. It is hypothesized that variant parasite type(s) might have been introduced to Sudanese cattle when they crossed to Ethiopia, a tsetse belt region.

A cross-sectional study was conducted between November 2009 and December 2009 in the riverbank of Abay river tributaries, located in three districts of Awi and Metekel zones, Northwest Ethiopia. The prevalence of bovine trypanosomosis, associated risk factors and distribution as well as vector identification in the study area were considered. Blood samples were collected from 540 randomly selected local (zebu) breed of cattle in nine peasant associations of three districts and the assumed risk factors were recorded. The collected samples were examined using hematological and parasitological techniques. In this study, sixty-seven animals (12.42%) were infected with different species of trypanosomes. Most of the infections were due to T. congolense (77.6%) followed by T. vivax (14.9%), T. brucei (6.0%) and mixed infection of T. congolense and T. vivax (1.5%). There was no statistical significance (p>0.05) between sex, age and coat color of skin, but significant differences were observed in body condition, altitude and districts (p<0.05). Mean PCV value of infected (19.42%) and non-infected (24.13%) group of animals had significant variation; and mean PCV value of poor body condition was significantly different (p<0.001) from good body condition. A total of 3072 tsetse flies of riverine species or palpalis group (Glossina tachinoides) and biting flies were caught, of these 2792 (90.9%) were tsetse flies and the remaining were Stomoxys and Tabanus. The overall apparent densities of tsetse and biting flies were 6.49 and 0.65flies/trap/day, respectively and the difference was significant (p<0.05). The study revealed that bovine trypanosomosis is more prevalent in low land and in poor body condition animals in the study area. Tsetse distribution also coincides with altitude, where there was high tsetse catch in low land, but none in mid land. Therefore, prompt control strategy has to be designed and implemented in the area to minimize the distribution of tsetse as well as trypanosomosis prevalence., (2010 Elsevier B.V. All rights reserved.)

In South American countries, trypanosomiasis as a result of Trypanosoma evansi and Trypanosoma vivax infections causes significant economic losses in livestock. The objectives of this study were to characterize the epidemiology of bovine trypanosomiasis in South America and to draw a comparison between South American and Asian T. evansi isolates based on the polymorphisms in their transferrin receptor encoding gene 6. We assessed the prevalence rates of T. evansi and T. vivax infections in cattle in different regions of Peru and Bolivia using the polymerase chain reaction (PCR) and found that, in Lima and Pucallpa in the Republic of Peru, T. evansi infection rates were 5.8% (6/104) and 2.5% (5/195), respectively, while in Santa Cruz, Republic of Bolivia, the infection rate for T. evansi was 11.5% (59/510). The prevalence rates of T. vivax in Lima and Santa Cruz were 3.8% (4/104) and 0.9% (5/510), respectively. In T. evansi, uptake of host transferrin is mediated by a receptor derived from the two expression site-associated genes 6 and 7 (ESAG6 and ESAG7). We previously showed that the ESAG6 depicts genetic diversity among different isolates of T. evansi in Asia. In this study, we cloned and sequenced the ESAG6 genes from T. evansi isolates from South America, and found, in addition to some of the previously observed variants, 20 novel variants of ESAG6 genes which could be categorized into three new clades among the various isolates. To conclude, the results obtained in this study suggest that T. evansi isolates from South America are more diverse than the Asian isolates.

This study was undertaken to detect Trypanosoma evansi infection in clinically ill cattle, buffaloes and horses that were suspected of 'surra' infection. Various diagnostic tests were utilized in order to assess the prevalence of infection in the clinically ill and 'suspected' animals. Animals in the Eastern Region of India were systematically studied for T. evansi infection, which had not been tested for previously. Examination of Giemsa-stained blood smears detected 5.3%, 9.4% and 40.6% infections; the mouse inoculation test detected 18.4%, 15.6% and 46.9% infections whereas an in-house ELISA detected anti-trypanosomal antibodies in 42.1%, 43.8% and 65.6% infections in clinically ill buffaloes, cattle and horses, respectively. It can be concluded that T. evansi is prevalent in cattle, buffaloes and horses in the Eastern Region of India.

Prevalence of bovine trypanosomosis was determined from a total of 203 blood samples collected from Butaleja district, eastern Uganda. All samples were examined by microhematocrit centrifuge test (MHC), PCR and ELISA. ELISA was performed in accordance with the OIE standard procedures using Trypanosoma brucei gambiense procyclic form crude antigens. PCR were utilized to identify the species and the subspecies of trypanosome. The overall prevalence of bovine African trypanosomosis was 8.9% by MHC, and 45.3% by the ELISA. Since substantial number (12 out of 18) of MHC positive samples were negative in the PCR tests, we could not conclude the most epidemic trypanosome species in the studied area. Nevertheless, the PCR results suggests that the most prevalent trypanosome was T. b. brucei (31/203), followed by T. congolense (6/203). In addition, only a few (3/203) mixed infections of T. b. brucei and T. congolense was detected by the PCR. Results obtained from this study indicates that bovine trypanosomosis is endemic in Butaleja district, Uganda.

Background & Objectives: The prevalence of trypanosomiasis was studied in cattle, being a major source of animal protein in Nigeria, thus, a very likely means of spread of Human African Trypanosomosis (HAT)., Methods: Enzyme-linked immunosorbent assay (ELISA) was used to diagnose bovine trypanosomiasis in 264 samples collected from adult cattle of mixed breeds, age and sex, in Anambra and Imo states, Nigeria., Results: Out of 264 samples analysed, 21 (7.96%) were seropositive for Trypanosoma congolense while 20 (7.58%) were seropositive for T. vivax and 8 (3.03%) were seropositive for T. brucei infections in both the states., Interpretation & Conclusion: The predominant species was found to be T. congolense. Mixed infection of three species, T. vivax, T. congolense and T. brucei was found to dominate other mixed infections in both the states. ELISA detected the infection of the three species of trypanosomes in the same group of animals. The usefulness of antigen capture ELISA in the diagnosis of human or animal trypanosomiasis was established, and the possibility of the spread of HAT caused by T. brucei gambiense and T.b. rhodesiense through cattle was expressed.

This study was focused on genetic diversity of Trypanosoma evansi which is a widely distributed haemoflagellate of veterinary importance that infects a variety of larger mammals including horses, mules, camels, buffalo, cattle and deer. The genetic diversity of T. evansi of beef cattle LAM19 was accomplished by using phylogenetic analysis based on internal transcribed spacer region (ITS). Blood sample was collected from a naturally infected beef cattle LAM 19 and parasitemia was raised by mouse inoculation. The parasites were collected and isolated by using DE 52 DEAE cellulose anion exchange column prior to DNA extraction. Upon PCR amplification of ITS region, the product of 1300bp in size was obtained. The ITS nucleotide sequences were analyzed and revealed that it could demonstrate the genetic diversity of T. evansi of beef cattle LAM19. Based on the ITS tree, beef cattle LAM 19 T. evansi were categorized into two main groups where the genetic diversity occurred within Group 1. The data could be applicable for the survey of parasite dynamics, epidemiological studies as well as prevention and control of the disease.

The sensitivity of LAMP, PCR and microscopy to detect Theileria spp. and Trypanosoma congolense in field-derived bovine blood samples from Tanzania was evaluated and compared. No parasites were detected by microscopy. Furthermore, no bovine Theileria spp. were detected by LAMP and PCR from all the 24 samples collected from Arusha. Four and one out of 24 samples were positive for Theileria congolense infection by LAMP and PCR respectively while, 18 and nine out of 40 samples from Dar es Salaam were positive by LAMP and PCR for Theileria spp. Infection, respectively. Although all samples from Dar es Salaam were negative for Trypanosoma congolense infections by PCR, 12 out of 40 samples were LAMP positive. Whilst PCR is an established gene amplification method for the detection of Theileria and trypanosome parasites, this study introduces LAMP as an alternative molecular diagnostic tool that could be used in large-scale epidemiological surveys.

Trypanosomosis caused by Trypanosoma vivax has been a constraint for cattle production in the Bolivian lowlands, since it was introduced in 1996. Flooded areas like the Bolivian Pantanal have a suitable environment for the presence and transmission of Salivarian trypanosomes and farmers from that region often report trypanosomosis-like problems on their farms. The objective of the present study, therefore, was to characterize the epidemiology of bovine trypanosomosis in the Bolivian Pantanal. In order to achieve this objective, 202 cattle from the province of Angel Sandoval and 209 cattle from the province of German Busch were randomly sampled (the Pantanal is located in both provinces). Twenty-nine farms in both provinces were visited, the farmers interviewed, and biologic samples collected from their cattle. Samples were submitted for parasitological and PCR evaluation and the prevalence of bovine trypanosomosis was estimated for each province. Laboratory results were correlated with the sampled animals packed cell volume (PCV) and body condition (BC) scores and the observed T. vivax parasites measured for morphometry analysis. Results from this study show differences in morphometric measures between T. vivax parasites from each province. Differences between provinces were also observed in the T. vivax-related disease situation. While in Angel Sandoval the PCV and BC of T. vivax-affected animals were significantly lower than those of the T. vivax-negative animals, in German Busch no differences were observed in the PCV and BC of T. vivax-positive or negative animals. Animal prevalence of T. vivax in Angel Sandoval was 27.79% (95% CI: 14.52-44.28) and in German Busch was 19.03% (95% CI: 9.19-30.75). The T. evansi animal prevalence in each province was 0.99% (95% CI: 0.27-2.99) and 5.71% (95% CI: 2.43-12.19), respectively. Based on questionnaire and laboratory results, it was concluded that trypanosomosis is a primary constraint for cattle production in the Bolivian Pantanal.

Direct PCR analysis of trypanosome infected blood samples in the quantities required for large scale epidemiological study has always been problematic. Current methods for identifying and differentiating trypanosomes typically require several species-specific reactions, many of which rely on mouse passaged samples to obtain quality concentrated genomic DNA. As a consequence important epidemiological information may be lost during the sample preparation stage. Here, we report a PCR methodology that reduces processing and improves on the sensitivity of present screening methods. The PCR technique targets the gene encoding the small ribosomal subunit in order to identify and differentiate all clinically important African trypanosome species and some subspecies. The method is more economical, simple, and sensitive than current screening methods, and yields more detailed information, thereby making it a viable tool for large-scale epidemiological studies.

A longitudinal epidemiological survey of bovine trypanosomosis and its vectors was carried out in the Volta river basin of Northern Ghana to determine the relationship between cattle management and the incidence of bovine trypanosomosis. Two groups of sentinel cattle under different systems of management, classified as "fully-sedentary" and "partially-sedentary" (depending on the type of management) were followed over a 1-year period starting from March 2003 onwards. Cattle were screened at intervals of 3 months using the buffy coat technique (BCT). Buffy coat specimen from animals that were positive for the BCT and those that were negative, but with a packed cell volume (PCV) of less than 21% were further tested using the polymerase chain reaction (PCR). Plasma from all animals were tested for antibody using the indirect antibody enzyme-linked immunosorbent assay (ELISA). Trypanosomosis challenge was determined in tandem with the epidemiological survey with watering sites of sentinel cattle being the foci of interest. The parasitological prevalence at the start of the survey was higher in the fully-sedentary group (9%) than in the partially-sedentary group (3%). In subsequent visits, however, the parasitological incidence was consistently higher in the partially-sedentary group than in the fully-sedentary group. The mean seroprevalence (ELISA) of both groups increased from 3% in March to 54% in December. Statistical analysis of the serological results using a random effect logistic regression, showed a significant difference in incidence of bovine trypanosomosis between the two groups. There was also a significant effect of time. The influence of cattle herding on host-vector-parasite interface and its consequence on the incidence of trypanosomosis are discussed.

A crossbred calf (3 months old) obtained from a farm where regular control of ticks was practised and found to be free of blood parasites was inoculated with 20 ml pooled blood collected from four field cattle which had very low Trypanosoma theileri parasitaemias (one parasite per 70 microl blood as determined by the haematocrit centrifugation technique). Trypanosoma theileri was present in the blood 6 days after injection and a peak parasitaemia of 42 parasites per 70 microl blood was recorded by day 12. Hyalomma anatolicum anatolicum nymphs were applied on the ears of the calf on day 8 and they dropped engorged by days 13 and 14. The resulting adult ticks were examined for the presence of T. theileri by severing a leg and making a smear of the clear haemolymph which exuded from the wound. The smear was fixed in methanol and stained with Giemsa stain. The infection rate with T. theileri in the ticks was 43.3% (26 out of 60). The intensity of infection was very high and various developmental stages of the flagellates were observed (epimastigotes, sphaeromastigotes, trypomastigotes and other intermediate stages). The haemolymph from 12 ticks was also collected in tissue culture medium and the trypanosomes survived for 25 weeks before eventually dying. The results demonstrated unequivocally the high vectorial capacity of the tick H. a. anatolicum for T. theileri.

The use of a single restriction fragment length polymorphism (RFLP)-PCR assay which is able to characterise all important bovine trypanosome species was evaluated for the detection of mixed infections with Trypanosoma brucei brucei, Trypanosoma theileri, Trypanosoma congolense and Trypanosoma vivax. Results showed that mixed infections are detectable at a minimum ratio of 2%/98% of standardised DNA solutions with a concentration of 10 ng ml(-1). All mixed infections gave clear profiles that could be easily differentiated except with T. theileri and T. congolense where the T. theileri band was concealed by the T. congolense profile.

The clinical, parasitological and molecular diagnosis of bovine trypanosomosis were compared using samples from 250 zebu cattle exposed to natural trypanosome challenge in Uganda. Clinical examination, molecular and parasitological diagnoses detected 184 (73.6%), 96 (38.4%) and 36 (14.4%) as diseased, respectively. The sensitivity and specificity of clinical examination were 87.5% and 35%, and 78 % and 27 % based on molecular and parasitological diagnoses, as gold standards, respectively. Of the 33, 3, 13 and 12 parasitological-positive cattle that had Trypanosoma brucei, Trypanosoma congolense, Trypanosoma vivax or mixed infections, 78 %, 33 %, 84 % and 100 % respectively manifested clinical signs. Of the 24, 89, 12, 3, 6 and 27 cattle detected by molecular diagnosis to have mixed infections, T. brucei, T. vivax, T. congolense forest-, Savannah- and Tsavo-type, 100%, 83%, 91%, 100%, 67% and 81 % had clinical signs, respectively. In conclusion, treatment of cattle based on clinical examination may clear up to 87.5 % or 78 % of the cases that would be positive by either molecular or parasitological diagnosis, respectively. Under field conditions, in the absence of simple and portable diagnostic tools or access to laboratory facilities, veterinarians could rely on clinical diagnosis to screen and treat cases of bovine trypanosomosis presented by farmers before confirmatory diagnosis in diagnostic centres for few unclear cases is sought.

A single polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay was used to characterise all important bovine trypanosome species. This is the first report of a sensitive pan-trypanosome PCR assay amplifying all species including T. vivax to a comparable extent using a single primer pair. A semi-nested PCR approach resulted in the detection of one T. congolense trypanosome genome/40 microl of blood, applied as buffy coat on filter paper. Restriction enzyme analysis using Msp1 and Eco571 gave a clear distinction between T. congolense, T. brucei, T. vivax and T. theileri. Several subgroups within the T. congolense group could be distinguished but no differences between the species belonging to the subgenus Trypanozoon or between T. simiae and T. theileri could be found. The use of MboII restriction enzyme allowed differentiation between T. simiae and T. theileri. The potential of the essay to be used as a suitable diagnostic tool is discussed.

Attempts were made to improve the accuracy of an antibody-detection ELISA for the detection of Trypanosoma evansi infection in cattle by improving the method of preparation of the crude antigen used. An IgG-ELISA was performed with five different antigen preparations: crude soluble antigen, soluble and insoluble fractions of crude antigen treated with 0.1% formalin and whole formalin-fixed trypanosomes treated with either trypsin or 2-mercaptoethanol. An IgM-ELISA using crude soluble antigen was also performed. Each ELISA was evaluated using serum from 44 Indonesian cattle infected with T. evansi and 262 uninfected cattle from Australia. There was no significant difference between the sensitivity or specificity of the IgG-ELISA using each of the five antigens. The IgM-ELISA using a crude untreated lysate was significantly less sensitive (p<0.05) than the IgG-ELISA using the same antigen, trypsin-treated antigen or the 0.1% formalin-treated soluble antigen (68, 64 and 64%, respectively). These results show that these modifications to the method of producing crude antigens for the Ab-ELISA does not improve the accuracy of diagnosis of T. evansi infection in cattle.

Research was undertaken to critically evaluate parasitological tests for the detection of Trypanosoma evansi in blood. The relative sensitivity of mouse inoculation (MI), the haematocrit centrifugation technique (HCT) and a modified miniature anion-exchange centrifugation technique (MAECT) were compared using blood and buffy coat. The effect that storage of blood prior to inoculation into mice has on the reliability of the MI test was also evaluated. The tests may be ranked in increasing order of sensitivity: HCT, MAECT with whole blood, MI with whole blood, MAECT with buffy coat and MI with buffy coat. The latter was able to detect 1.25 T. evansi per 4ml of blood. The reliability of the MI test was not reduced with storage of blood containing at least 25 T. evansi per ml for up to 21h prior to inoculation into mice. These results demonstrate that sensitivity of the MI and MAECT are increased approximately 10-fold through the use of buffy coat in place of whole blood. Although, the MI is marginally more sensitive MAECT is better suited to field use.

No sleeping sickness or nagana cases have been reported in Botswana since 1985. In view of several confirmed clinical cases of nagana and reports of heavy bovine mortality, a parasitological survey was conducted to determine the prevalence of trypanosome infection in cattle in Maun and Shakawe areas of Ngamiland district. Wet blood films, buffy coat and Giemsa-stained thick and thin blood smears were used to detect trypanosomes in animals. Overall,trypanosome infection rate was 15.98%, with 5.94% and 27.29% in Maun and Shakawe respectively. The urgent need to combat trypanosomosis in Ngamiland, particularly in the Shakawe area, is highlighted, and a 3-phase integrated tsetse control strategy for this disease problem is discussed.

A tsetse and bovine trypanosomosis survey was conducted during 1998 and 1999 in the Matutuine District of Maputo Province (Mozambique). A total of 59 Glossina brevipalpis and 17 Glossina austeni were captured throughout the district. Survey results suggest that Glossina brevipalpis is mainly concentrated in dense vegetation along the Maputo River and in the wetlands east of the river. G. austeni, on the other hand, was captured mainly in dense thickets in drier areas. Both tsetse species are suspected to be vectors of bovine trypanosomosis. Bovine trypanosomosis (75,5% Trypanosoma congolense) was diagnosed in 53 animals (13,9%) from seven sampling sites distributed throughout the district. The prevalence of cattle with anti-trypanosomal antibodies was high (29,9%). The incidence of trypanosomal infections in sentinel cattle was also high. The widespread distribution of bovine trypanosomosis and the high prevalence of infection are likely to have a significant impact on cattle production and, hence, the cattle restocking exercise in the district.

African animal trypanosomoses constitute the most important vector-borne cattle diseases in sub-Saharan Africa. Generally it is considered that there is a great lack of accurate tools for the diagnosis of the disease. During a trypanosomosis survey in the agro-pastoral zone of Sideradougou, Burkina Faso, 1036 cattle were examined for trypanosomes using microscopy. The PCR was applied on a subset of 260 buffy-coat samples using primers specific for Trypanosoma congolense savannah and riverine-forest groups, T. vivax, and T. brucei. Parasitological examination and the molecular technique were compared, showing a better efficiency of the latter. In the near future, the PCR is likely to become an efficient tool to estimate the prevalence of African trypanosomoses in affected areas.

Investigations to identify the causes of high mortalities in cattle in the agropastoral zone (ZAP) of Yalé started in March 1993. African animal trypanosomosis (AAT) was found to be the major constraint, with incidence rates exceeding 30%, justifying a tsetse control programme, which started in March/ April 1994. The treatment of all cattle at bimonthly intervals with deltamethrin 1% pour on and the display of 1500 insecticide impregnated targets during the 6 months of the dry season each year helped to reduce the tsetse populations (Glossina tachinoides and G. morsitans submorsitans) by more than 90%. In less than 7 months, the incidence of AAT dropped below 5% and remained there throughout the intervention until June 1996, in spite of an increase to 3 months in the interval between the treatments. Mean PCV values increased significantly from 26.5-30.9%, before, to 30.7-36.3% during the intervention. The improvement in the overall health resulted in a resumption in fertility and milk production, allowing the sale of dairy products in Léo, thus creating a gross income of about $US3/day for the Fulani women.

A multidisciplinary work was undertaken in the agropastoral zone of Sidéradougou, Burkina Faso to try to elucidate the key factors determining the presence of tsetse flies. In this study the PCR was used to characterize trypanosomes infecting the vector (Glossina tachinoides and Glossina palpalis gambiensis) and the host, i.e. cattle. A 2-year survey involved dissecting 2211 tsetse of the two Glossina species. A total of 298 parasitologically infected tsetse were analysed by PCR. Trypanosoma vivax was the most frequently identified trypanosome followed by the savannah type of T. congolense and, to a lesser extent, the riverine forest type of T. congolense, and by T brucei. No cases of T. simiae were found. From the 107 identified infections in cattle, the taxa were the same, but T. congolense savannah type was more frequent, whereas T. vivax and T. congolense riverine forest types were found less frequently. A correlation was found between midgut infection rates of tsetse, nonidentified infections and reptile bloodmeals. These rates were higher in G.p. gambiensis, and in the western part of the study area. T. vivax infections were related to cattle bloodmeals, and were more frequent in G. tachinoides and in the eastern study area. The PCR results combined with bloodmeal analysis helped us to establish the relationships between the vector and the host, to assess the trypanosome challenge in the two parts of the area, to elucidate the differences between the two types of T. congolense, and to suspect that most midgut infections were originating from reptilian trypanosomes.

During the late rainy season and winter season in 1990, outbreaks of suspected trypanosomiasis in native cattle (Bos indicus) occurred on 13 farms in Petchaboon province, Thailand. Forty-two cattle presented with nervous symptoms including circling, excitation, jumping, aggressive behavior, lateral recumbency, convulsion and finally death. Blood samples from 39 cattle on the two farms in which the outbreaks occurred were collected and examined for the presence of Trypanosoma evansi. It was found that all 16 blood samples from cattle on farm A were positive of T. evansi by mouse inoculation and indirect fluorescent antibody test (IFAT). In cattle from farm B, on the other hand only 37.5% and 39% of the samples were positive by mouse inoculation and IFAT, respectively. T. evansi was detected on impression smears of organs from the three cattle which died with nervous symptoms and also in smears made from their cerebrospinal fluid. In addition, trypanosomes were isolated from the cerebrum, cerebellum, pons and spinal cord by mouse inoculation.

Two studies on the efficacy of mel Cy (Cymelarsan, Rhone Merieux, France) for the treatment of cattle infected with Trypanosoma evansi were carried out with groups of 5 Friesian Holstein calves infected with an Indonesian stock of T. evansi and treated 14 days after infection. In the first study 3 groups were injected subcutaneously with Cymelarsan at dose rates of 0.125, 0.25 and 0.50 mg/kg and in the second study 2 i/m at 0.50 and 0.75 mg/kg. The response to treatment was monitored parasitologically by daily microhaematocrit centrifugation technique and weekly mouse inoculation. Enzyme linked immunosorbent assays were used to monitor trypanosomal antibodies and trypanosomal antigens in serum samples collected weekly. Relapse infections occurred in all the groups given the drug s/c whilst all the animals treated i/m remained parasitologically negative up to 80 days after treatment. Results from serological assays, however, suggested the possible persistence of trypanosome infection in the animals treated at a dose rate of 0.50 mg/kg i/m although trypanosomes could not be demonstrated parasitologically. A dose rate of 0.75 mg/kg administered i/m is recommended, therefore, for the treatment of T. evansi infection in Friesian Holstein cattle.

Relatively simple protocols employing non-radioactive DNA probes have been used for the detection of African trypanosomes in the blood of mammalian hosts and the saliva of live tsetse flies. In combination with the polymerase chain reaction (PCR), the protocols revealed trypanosomes in buffy-coat samples from antigenaemic but aparasitaemic cattle and in the saliva of live, infected tsetse flies. Furthermore, the protocols were used to demonstrate concurrent natural infections of single tsetse flies with different species of African trypanosomes.

A comparison of the symptomatology, haematology and prevalence of trypanosomiasis in Holstein Friesian and White Zebu cattle exposed to natural infections on a ranch in a rain forest zone of Nigeria is presented. 23 (44%) of the adult Friesians had trypanosome infections with a generally heavy parasitaemia. Infection was light in the Friesian calves and the Zebus with infection rates of 2 (6.9%) and 3 (15%) respectively. Trypanosoma vivax was the sole species encountered on the farm. There was a general unthrifty appearance in the adult Friesian herd as well as classical signs of trypanosomiasis. The Friesian calves and Zebus were generally in good conditions with an appearance of good health except one each of the infected animals which showed apparent symptoms of the disease. There was a marked reduction of the red cell values of the infected adult Friesian and Zebu cattle. The red cell values of the uninfected adult Friesians were equally depressed suggesting cryptic infections or that they were cured parasitologically by the recently administered trypanocide. The Friesian calves had normal red cell values for both the infected and uninfected. Leucocyte counts were generally high on the Farm and higher for the infected animals.

Cattle (from 5 sites in Louisiana) were examined by blood culture for the presence of Trypanosoma theileri. A prevalence of 81% was found in the 291 cattle examined. A greater number of beef cattle (93%) than dairy cattle (73%) was infected. Differences in prevalence in cattle from different regions of the state were not noted.

The double microcentrifugation technique, described by KRATZER and ONDIEK (1989) for the parasitological diagnosis of trypanosomes, has been tested both in the laboratory and in the field. The limits of detection obtained here were not as low as those described in the original experiment, but the sensitivity of this technique for the detection of Trypanosoma brucei, T. congolense and T. vivax was better than the phase contrast buffy coat method. This technique, which is easy to apply in the field, is highly recommended, especially for epidemiological surveys. A protocol and a list of equipment are included.