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In 2018, extensive field studies of diversity and prevalence of helminth infection in synanthropic rodents and non-rodent small mammals from public parks and citified areas in the Bangkok Metropolitan were conducted. Rattus rattus complex was the dominant small mammal in public parks. Of the 197 animals, 147 individuals were infected with one or more species of helminths, yielding an infection prevalence of 74.6%. Twenty-five species of helminths were recovered during necropsy. Pterygodermatites tani was the most prevalent (36.2%); other encountered species included Raillietina celebensis, Hydatigera taeniaformis (metacestode in liver tissue), Gongylonema neoplasticum and Hymenolepis diminuta. Different helminth assemblages infected three different host taxa, i.e. synanthropic Rattus spp., Tupaia belangeri (Northern treeshrew) and Suncus murinus (Asian house shrew). Nine species of possible zoonotic helminths were identified. The focus on synanthropic rats influenced the findings of helminth diversity by either host intrinsic or extrinsic factors. A significant positive correlation was found between host body mass and helminth species richness. Greater helminth species richness was found in rats from public parks compared with animals from citified areas (e.g. inside buildings or offices). Also, helminth species richness was negatively correlated with the proportion of post-flooding/rain-fed land. These results provide essential information for assessing the incidence of potential zoonotic health threats in Bangkok and updating research in parasite ecology. [ABSTRACT FROM AUTHOR]

The ultrastructural characteristics of the mature spermatozoon of Diplodiscus amphichrus (Digenea, Paramphistomoidea, Diplodiscidae) and their ultrastructural organisation were examined by means of transmission electron microscopy. Live digeneans were collected from the Chinese edible frog Hoplobatrachus rugulosus in Thailand. The male gamete of D. amphichrus is a filiform cell with two axonemes of the 9 + '1' trepaxonematan pattern, nucleus, one mitochondrion, parallel cortical microtubules, a well-developed lateral expansion, external ornamentation of the plasma membrane, spine-like bodies, and granules of glycogen. These ultrastructural characteristics have already been described in other paramphistomoids studied so far except for the cladorchiids, which present some differences. Two characteristics of the male gamete of D. amphichrus were found for the first time in a digenean: (i) the appearance of the initial part of the lateral expansion before the axonemes in the anterior extremity and (ii) the separation between the second axoneme and the nucleus in the posterior tip. Our results are compared with the available data in the Digenea and particularly with other paramphistomoids. [ABSTRACT FROM AUTHOR]

Commercial small-scale chicken farms managed as all-in-all-out but operating with low standards of hygiene/biosecurity are increasingly common in Vietnam. These conditions facilitate the transmission of gastrointestinal helminths. However, there are no published data on helminths in these systems. We aimed (1) to determine the prevalence/burden of gastrointestinal helminths in small-scale commercial flocks in the Mekong Delta region and (2) to investigate the association between worm burdens and birds' weight and disease status. Randomly selected chickens (n = 120) from 'normal' flocks were investigated at the end of their production cycle (~ 18 weeks), as well as 90 chickens from 'diseased' flocks with signs of respiratory and/or severe disease. The gastrointestinal tract of chickens was dissected and all visible helminths were identified and counted. A total of 54.2% and 54.4% normal and diseased chickens contained helminths. Among colonised birds, the diseased ones harboured a higher mass of helminth worms than normal (healthy) birds (3.8 ± SD 8.6 g vs. 1.9 ± SD 6.3 g, respectively). Eight species were identified, including nematodes (Ascaridia galli, Cheilospirura hamulosa and Heterakis gallinarum), cestodes (Hymenolepis, Raillietina cesticillus, Raillietina echinobothrida, Raillietina tetragona,) and one trematode (Echinostomatidae). Heterakis gallinarum was the most prevalent helminth (43.3% and 42.2% in normal and sick chickens, respectively), followed by A. galli (26.7% and 41.1%). Colonised chickens weighed 101.5 g less than non-colonised birds. Colonisation was higher during the rainy months (May–November) for both H. gallinarum and A. galli. Anthelminthic usage was not associated with reduced helminth burdens. We recommend upgrading cleaning and disinfection and limiting access to ranging areas to control helminths in small-scale chicken flocks. [ABSTRACT FROM AUTHOR]

More than a dozen Gongylonema spp. (Spirurida: Spiruroidea: Gongylonematidae) have been described from a variety of rodent hosts worldwide. Gongylonema neoplasticum (Fibiger & Ditlevsen, 1914), which dwells in the gastric mucosa of rats such as Rattus norvegicus (Berkenhout) and Rattus rattus (Linnaeus), is currently regarded as a cosmopolitan nematode in accordance with global dispersion of its definitive hosts beyond Asia. To facilitate the reliable specific differentiation of local rodent Gongylonema spp. from the cosmopolitan congener, the genetic characterisation of G. neoplasticum from Asian Rattus spp. in the original endemic area should be considered since the morphological identification of Gongylonema spp. is often difficult due to variations of critical phenotypical characters, e.g. spicule lengths and numbers of caudal papillae. In the present study, morphologically identified G. neoplasticum from 114 rats of seven species from Southeast Asia were selected from archived survey materials from almost 4,500 rodents: Thailand (58 rats), Cambodia (52 rats), Laos (three rats) and Philippines (one rat). In addition, several specimens from four rats in Indonesia were used in the study. Nucleotide sequences of the ribosomal RNA gene (rDNA) (5,649 bp) and the cytochrome c oxidase subunit 1 gene (cox1) (818 bp) were characterised. The rDNA showed little nucleotide variation, including the internal transcribed spacer (ITS) regions. The cox1 showed 24 haplotypes, with up to 15 (1.83%) nucleotide substitutions regardless of parasite origin. Considering that Rattus spp. have been shown to originate from the southern region of Asia and G. neoplasticum is their endogenous parasite, it is reasonable to propose that the present study covers a wide spectrum of the genetic diversity of G. neoplasticum, useful for both the molecular genetic speculation of the species and the molecular genetic differentiation of other local rodent Gongylonema spp. from the cosmopolitan congener. [ABSTRACT FROM AUTHOR]

The present study records the ultrastructural organization of the mature spermatozoon of Opisthorchis viverrini by means of transmission electron microscopy. The spermatozoon of O. viverrini is a filiform cell, tapered at both extremities. It exhibits the characteristics of type IV spermatozoon of digeneans, namely with two axonemes of the 9+'1' trepaxonematan pattern, external ornamentation of the plasma membrane associated with cortical microtubules that are in the posterior part of the anterior region of the sperm cell, and with two mitochondria. The maximal number of cortical microtubules is in the anterior part of the spermatozoon and arranged into two bundles. Other characteristics are spine-like bodies and a posterior extremity with only the second axoneme. Ultrastructural characters of the spermatozoon of O. viverrini are compared with those of other known digeneans belonging to the Opisthorchioidea, with particular emphasis on representatives of the family Opisthorchiidae. The main differences between O. viverrini and its congener Opisthorchis felineus are the spine-like bodies (present and absent, respectively) and the posterior spermatozoon character (axoneme and nucleus, respectively). [ABSTRACT FROM AUTHOR]

Whipworms were collected from rodents (Muridae) from six West African countries: Burkina-Faso, the Islamic Republic of Mauritania, and the Republics of Benin, Guinea, Mali and Senegal. Molecular sequences (ITS-1, 5.8S and ITS-2 of the ribosomal DNA gene) and morphometric characters were analysed in Trichuris (Nematoda: Trichuridae) specimens found in seven host species: Arvicanthis niloticus, Gerbilliscus gambianus, Gerbillus gerbillus, G. tarabuli, Mastomys erythroleucus, M. huberti and M. natalensis. Phylogenetic analyses revealed three clades, one recognised as Trichuris mastomysi, previously recorded in M. natalensis from Tanzania, and the other two previously undescribed. A new species named Trichuris duplantieri n. sp., found in Gerbillus spp. from Mauritania, was characterised using molecular and morphometric methods. [ABSTRACT FROM AUTHOR]

A new species of filarioid nematode of the genus Breinlia Yorke & Maplestone, 1926 (Nematoda: Filarioidea) is described from rodents in Lao PDR and according to its morphology, is placed in the subgenus Breinlia. Breinlia ( Breinlia) jittapalapongi n. sp. occurs in the Asian house rat ( Rattus tanezumi Temminck) and the Sikkim rat ( Rattus andamanensis Blyth) and is reported from two localities (Luang Prabang and Champasak). The new species can be distinguished from all other congeners, which are mostly distributed in Australasia (twenty-two species), South East Asia (four species) and India (two species), by the following characters of the males: shape and size of gubernaculum, length of spicules, pattern of cloacal papillae and presence of sclerotised ring in the buccal capsule. This is the fifth species of Breinlia described from South East Asia. [ABSTRACT FROM AUTHOR]

Southeast Asia is a biodiversity hotspot that harbours many species of rodents, including some that live in close contact with humans. They host helminth parasites, some of which are of zoonotic importance. It is therefore important to understand the factors that influence the richness of the helminths parasitizing rodents. The specific objectives of this study were to evaluate rodent species as a factor determining helminth richness in rodent assemblages, to identify the major rodent helminth reservoir species and to explore the influence of habitat on helminth richness. We estimated helminth species richness using a large dataset of 18 rodent species (1,651 individuals) originating from Southeast Asia and screened for helminth parasites. The use of an unbiased estimator shows that the helminth species richness varies substantially among rodent species and across habitats. We confirmed this pattern by investigating the number of helminth species per individual rodent in all rodent species, and specifically in the two mitochondrial lineages Rattus tanezumi and R. tanezumi R3, which were captured in all habitats. [ABSTRACT FROM AUTHOR]

Heterakis is a genus of parasitic nematodes, the majority of which are found in ground-feeding birds and only rarely in mammals. The best-known species is Heterakis spumosa, a parasite associated with the cosmopolitan invasive rodent Rattus rattus of Asiatic origin. Heterakis dahomensis was described in 1911 as a parasite of the Gambian giant rat ( Cricetomys gambianus) from Benin (Africa), subsequently synonymized to H. spumosa by Hall (1916). The study of helminths in African rodents is scarce and patchy. Since the original description of H. dahomensis, there have been only a few reports from Africa of species belonging to the genus Heterakis and the validity of this species has never in fact been confirmed or rejected. In the present study individual Heterakis spp. were collected from C. gambianus from Senegal. The morphological data taken point to differences between Heterakis dahomensis and H. spumosa, specifically in the number of tail papillae in males and in the vulva cuticular processes of females. In addition, molecular data revealed differences between these taxa and so H. dahomensis should be considered as a valid species. Moreover, recent changes in the systematics of the genus Cricetomys mean that it is now necessary to study the morphology and genetics of the Heterakis specimens collected from Cricetomys spp. (previously assigned to C. gambianus) in order to determine their taxonomic status as either H. dahomensis o H. spumosa. [ABSTRACT FROM AUTHOR]

Sex-biased parasitism is rarely investigated in relation to host tolerance and resistance, which are two defense strategies hosts can adopt when challenged by parasites. Health or fitness deteriorations in less tolerant individuals with increasing parasite burden would be faster than those in more tolerant ones. Hence, the body condition and reproductive potential of an infected individual host can be considered proxies for tolerance to parasitism. We studied Mediterranean populations of the wood mouse ( Apodemus sylvaticus) and its helminth parasites. We assessed their resistance using the phytohemagglutinin test and spleen size, and their tolerance using body condition in males and females and testes mass in males. In order to avoid spurious correlations, we took into account the phylogeographic structure of the Mediterranean wood mouse populations. We used a mixed model adapted from the animal model used in quantitative genetics. While helminth infection did not differ between the two sexes, females and males differed in their measured defenses. Females seem to invest more in immune defense with increasing risk of parasite diversity, but also appear to be potentially more tolerant of parasitic diversity. These results suggest the existence of sexual differences in resistance and tolerance, and that measurements of parasitic loads alone could be insufficient to detect any underlying sexual differences in the two strategies that have evolved in response to multiple parasitic attacks. [ABSTRACT FROM AUTHOR]

A large number (828) of rodents belonging to nine genera ( Bandicota, Berylmys, Chiropodomys, Hapalomys, Leopoldamys, Maxomys, Mus, Niviventer and Rattus) were trapped in four Thai provinces between 2008 and 2010. A new species of Protospirura (Nematoda: Spiruridae) was identified and described. Protospirura siamensis n. sp. was found in 10 rodent species from the four Thai provinces surveyed. The new species can be distinguished from known species of the genus by the arrangement of the papillae on the male and the morphology and length of the spicules. This is the first species of Protospirura to be described from South-East Asia. [ABSTRACT FROM AUTHOR]

The helminths of two sympatric species of rodents, the striped field mouse Apodemus agrarius and the yellow-necked mouse, Apodemus flavicollis from Slovakia were studied to determine whether there are similarities in the composition of the helminth fauna of two closely related host species living in the same area. A total of twelve species of helminths were identified in these rodent populations, including Brachylaima sp. (Trematoda); Hymenolepis diminuta (Rudolphi, 1819), Mesocestoides sp. larvae, Rodentolepis fraterna (Stiles, 1906), Rodentolepis straminea (Goeze, 1782), Skrjabinotaenia lobata (Baer, 1925), Taenia taeniaeformis larvae (Batsch, 1786) (Cestoda); Aonchotheca annulosa (Dujardin, 1845), Heligmosomoides polygyrus (Dujardin, 1845), Heterakis spumosa Schneider, 1866, Mastophorus muris (Gmelin, 1790) and Syphacia stroma (Linstow, 1884) (Nematoda). In A. agrarius, H. polygyrus was the most prevalent, as well as the most abundant helminth, but R. fraterna was the species with the highest mean intensity. In contrast, S. stroma dominated the A. flavicollis helminth fauna with the highest prevalence, mean abundance and mean intensity. Both rodent populations harboured nine helminth species, although the mean individual species richness was significantly higher in A. agrarius than in A. flavicollis. The analysis of helminth diversity at both component and infracommunity levels revealed differences between the two rodent populations, which are most likely attributable to the specific host ecology. [ABSTRACT FROM AUTHOR]

Host immunocompetence assessed by spleen size and response to phytohaemagglutinin (PHA) injection may give some indications on the control of parasite infection and on host mediation effect, through immunity, on parasite community structure. We investigated the helminth community and immunocompetence of the white-toothed shrew in a small area to test the relationship between immunocompetence and intensity of helminth infection. At the proximate level and if spleen mass and PHA response reflect the level of immunocompetence, we expected that individuals with a large spleen or a high PHA response should harbour a lower parasite load than individuals with relatively small spleen or low PHA response. In addition, we predicted that the structure of the helminth community should be mediated by the host’s immune defence. Spleen mass was linked to helminth infection. Nematodes and cestodes were negatively associated within hosts. PHA response was not related to total helminth intensity of infection but was negatively related to cestode intensity and positively to nematode intensity. This result suggests either a differential modulating effect on immunity by the two groups of worms or the existence of an antagonistic association between nematodes and cestodes mediated by the immune response of the host. [ABSTRACT FROM AUTHOR]

We investigate the determinants of macroparasite species richness of Iberian carnivores. For this, we used the parasitological data collected on 14 species of carnivores over a 10-year period. These previously unpublished data permitted to estimate parasite species richness using estimators of species richness, i.e. Jackknife first order and Chao 2. Most of the parasite species were rare, with low prevalence. Potential determinants were investigated as possible factors explaining the variability of parasites species richness among carnivores host body mass, host geographical range, host longevity and host density. Using independent contrasts, we found positive relationships between residuals of estimates of parasite species richness and residuals in host density, and between residuals of estimates of parasite species richness and residuals in host range. These results are discussed in terms of risk of extinction and invasion abilities related to a possible investment in immune defences correlated with parasite diversity. [ABSTRACT FROM AUTHOR]