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Background: Information on human filariasis in international travelers is scarce. We describe the epidemiology, clinical presentation, and outcome of these infections in a reference travel clinic over the past decades., Methods: We reviewed all cases of filariasis diagnosed at the Institute of Tropical Medicine, Antwerp, Belgium, from 1994 to 2018. Diagnosis was obtained by either parasitological methods (confirmed) or strict clinical case definitions (probable). We assessed the characteristics of cases at diagnosis and response to therapy within 3-12 months., Results: A total of 320 patients (median age: 41 years; 71% males) were diagnosed with 327 filarial infections (Wuchereria bancrofti = 6, Onchocerca volvulus = 33, Loa loa = 150, Mansonella perstans = 130, unspecified species = 8). Diagnosis was confirmed in 213/320 (67%) patients. European long-term travelers accounted for 166 patients (52%) and visitors/migrants from tropical countries for another 110 (34%). Central Africa was the likely region of acquisition for 294 (92%) patients. The number of filariasis cases decreased from 21.5/year on average in the 1990s to 6.3/year in the past decade, when loiasis became predominant. Cases reported symptoms in >80% of all filarial infections but mansonellosis (45/123 single infections; 37%). Lymphatic filariasis and onchocerciasis cases responded well to conventional therapy. However, 30% of patients with loiasis and mansonellosis experienced treatment failure (with diethylcarbamazine and levamisole-mebendazole, respectively)., Conclusions: The burden and species distribution of filariasis in travelers evolved in the past decades. Most presentations were symptomatic. Case management would benefit from more effective therapies for loiasis and mansonellosis., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Human filariae are vector-borne parasites and the causative agents of various diseases, including human onchocerciasis and lymphatic filariasis. Onchocerciasis causes a spectrum of cutaneous and ophthalmologic manifestations (including blindness) and has long been a major public health problem in Bioko Island (Equatorial Guinea). Bioko Island has been included in the WHO's Onchocerciasis Control Program since 1987. In Bioko Island, the specificity and sensitivity of clinical Onchocerca volvulus diagnosis is key. The objective of this work was to update onchocerciasis elimination progress in Bioko Island, after 18 years of mass ivermectin intervention, and the general filariasis situation through a rapid and accurate molecular method. A cross-sectional study was conducted in Bioko Island from mid-January to mid-February 2014. A total of 543 subjects were included in the study. Whole blood and one skin snip (from lumbar regions) were analysed with a real time PCR assay. Two other skin biopsies were analysed by an expert microscopist. All positive samples were confirmed by sequencing. Traditional microscopic examination of the skin biopsies failed to detect any microfilariae. However, 11 (2.03%) infections were detected using PCR assay, including one O. volvulus, two Mansonella streptocerca, seven Mansonella perstans and one Loa loa infections. PCR assays in blood detected 52 filariae-positive individuals (9.6%) which harboured M. perstans or L. loa. The low prevalence of O. volvulus confirms the success of the Onchocerciasis Control Programme and suggests that Mass Drug Administration in Bioko Island can be interrupted in the near future. The very high prevalence of M. perstans found in skin snips assays raises doubts about the reliability of microscope-based diagnosis of O. volvulus infections., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Mansonella perstans is a widespread, but relatively unknown human filarial parasite transmitted by Culicoides biting midges. Although it is found in many parts of sub-Saharan Africa, only few studies have been carried out to deepen the understanding of its ecology, epidemiology, and health consequences. Hence, knowledge about ecological drivers of the vector and parasite distribution, integral to develop spatially explicit models for disease prevention, control, and elimination strategies, is limited., Methodology: We analyzed data from a comprehensive nationwide survey of M. perstans infection conducted in 76 schools across Uganda in 2000-2003, to identify environmental drivers. A suite of Bayesian geostatistical regression models was fitted, and the best fitting model based on the deviance information criterion was utilized to predict M. perstans infection risk for all of Uganda. Additionally, we investigated co-infection rates and co-distribution with Wuchereria bancrofti and Plasmodium spp. infections observed at the same survey by mapping geographically overlapping areas., Principal Findings: Several bioclimatic factors were significantly associated with M. perstans infection levels. A spatial Bayesian regression model showed the best fit, with diurnal temperature range, normalized difference vegetation index, and cattle densities identified as significant covariates. This model was employed to predict M. perstans infection risk at non-sampled locations. The level of co-infection with W. bancrofti was low (0.3%), due to limited geographic overlap. However, where the two infections did overlap geographically, a positive association was found., Conclusions/significance: This study presents the first geostatistical risk map for M. perstans in Uganda. We confirmed a widespread distribution of M. perstans, and identified important potential drivers of risk. The results provide new insight about the ecologic preferences of this otherwise poorly known filarial parasite and its Culicoides vector species in Uganda, which might be relevant for other settings in sub-Saharan Africa.

Background: Immunochromatographic card test (ICT) is a tool to map the distribution of Wuchereria bancrofti. In areas highly endemic for loaisis in DRC and Cameroon, a relationship has been envisaged between high L. loa microfilaria (Mf) loads and ICT positivity. However, similar associations have not been demonstrated from other areas with contrasting levels of L. loa endemicity. This study investigated the cross-reactivity of ICT when mapping lymphatic filariasis (LF) in areas with contrasting endemicity levels of loiasis and mansonellosis in Cameroon., Methodology/principal Findings: A cross-sectional study to assess the prevalence and intensity of W. bancrofti, L. loa and M. perstans was carried out in 42 villages across three regions (East, North-west and South-west) of the Cameroon rainforest domain. Diurnal blood was collected from participants for the detection of circulating filarial antigen (CFA) by ICT and assessment of Mf using a thick blood smear. Clinical manifestations of LF were also assessed. ICT positives and patients clinically diagnosed with lymphoedema were further subjected to night blood collection for the detection of W. bancrofti Mf. Overall, 2190 individuals took part in the study. Overall, 24 individuals residing in 14 communities were tested positive by ICT, with prevalence rates ranging from 0% in the South-west to 2.1% in the North-west. Lymphoedema were diagnosed in 20 individuals with the majority of cases found in the North-west (11/20), and none of them were tested positive by ICT. No Mf of W. bancrofti were found in the night blood of any individual with a positive ICT result or clinical lymphoedema. Positive ICT results were strongly associated with high L. loa Mf intensity with 21 subjects having more than 8,000 L. loa Mf ml/blood (Odds ratio = 15.4; 95%CI: 6.1-39.0; p < 0.001). Similarly, a strong positive association (Spearman's rho = 0.900; p = 0.037) was observed between the prevalence of L. loa and ICT positivity by area: a rate of 1% or more of positive ICT results was found only in areas with an L. loa Mf prevalence above 15%. In contrast, there was no association between ICT positivity and M. perstans prevalence (Spearman's rho = - 0.200; p = 0.747) and Mf density (Odds ratio = 1.8; 95%CI: 0.8-4.2; p = 0.192)., Conclusions/significance: This study has confirmed the strong association between the ICT positivity and L. loa intensity (Mf/ml of blood) at the individual level. Furthermore, the study has demonstrated that ICT positivity is strongly associated with high L. loa prevalence. These results suggest that the main confounding factor for positive ICT test card results are high levels of L. loa. The findings may indicate that W. bancrofti is much less prevalent in the Central African region where L. loa is highly endemic than previously assumed and accurate re-mapping of the region would be very useful for shrinking of the map of LF distribution.

Ivermectin has been and continues to be extensively used to control onchocerciasis in areas of hyper and mesoendemicity within the African Programme of Onchocerciasis Control. As programmes to eliminate lymphatic filariasis (LF) caused by Wuchereria bancrofti expand, areas of coendemicity with onchocerciasis will be incorporated into LF programmes. This study reports that in villages which were hyperendemic for onchocerciasis after some 14 years of treatment with ivermectin, no W. bancrofti could be detected in a population of 1210 individuals whilst in adjacent villages a prevalence of around 3% was found. Despite the long period of ivermectin treatment Mansonella perstans did not appear to respond to ivermectin in this setting.

The purpose of this study is to document the potential feasibility of using a bed net impregnation program to enhance the control of Malayan filariasis in southern Thailand. A survey was conducted in one Muslim and one Buddhist village along the swamp forest in Narathiwat Province. Face-to-face interview was employed to collect data on practice of bed net use, knowledge and attitudes on filarial control and acceptance if a bed net impregnation program were to be introduced. Bed nets were used by 98.5% of the study households. Both Muslims and Buddhists were all in bed by 23.00 hrs. By 03.00 hrs, more than 20% of Buddhists were out of bed for rubber tapping, whereas more than 90% of the Muslim were still in bed until 04.30 hrs. Combining our data with biting rate from a previous study, approximately one-third of Mansonia bites were protected by the current bed net practice. The impregnation program was potentially welcome by both groups of villagers. From this study, we conclude that a bed net impregnation program in this area is feasible.

Baseline epidemiological investigations on lymphatic filariasis were conducted for the first time in Uganda in 3 communities in the districts of Lira (Alebtong area), Soroti (Lwala area) and Katakwi (Obalanga area), located to the north of Lake Kyoga at an altitude of 1000-1100 m above sea level. Individuals from the communities were examined, in April-August 1998, for Wuchereria bancrofti specific circulating antigen (by ICT card test), microfilaraemia (by counting chamber and stained blood-smear techniques) and chronic clinical manifestations of lymphatic filariasis. Endophilic mosquitoes were sampled and dissected for filarial larvae. Prevalences of circulating filarial antigen positivity were 29%, 18% and 30% in the Alebtong, Lwala and Obalanga communities, respectively. Microfilaria (mf) prevalences were 18%, 9% and 21%, and geometric mean mf intensities among mf-positive individuals were 306, 171 and 402 mf/mL blood, in the same communities. Examination of stained blood smears revealed mf of both W. bancrofti and Mansonella perstans, but more than 80% of mf-positive individuals harboured the first of these parasites. Prevalences of hydrocoele in adult (> or = 20 years) males were 28%, 7% and 17%, and prevalences of limb elephantiasis in adults were 9%, 4% and 4%, in the Alebtong, Lwala and Obalanga communities, respectively. Anopheles gambiae s.l. (mainly An. gambiae s.s.) and An. funestus were common in all 3 communities, and showed W. bancrofti infectivity rates of 1.1-1.7% and 1.3-2.9%, respectively. It is concluded that lymphatic filariasis is highly endemic in these high-altitude areas of Uganda, with An. gambiae s.l. and An. funestus being the main vectors.

In a nine-months epidemiological study to assess the status of human filariasis in north-western zone of Bauchi State, Nigeria, 3.5% prevalence was recorded in 8 communities. Of the 1536 persons examined, 54 were microfilaremic for three blood-dwelling filarial parasites. 22 (1.4%) were positive for Mansonella perstans, 10 (0.7%) and 22 (1.4%) had Loa loa and Wuchereria bancrofti respectively. W. bancrofti showed low microfilaremia in females of reproductive age with high degree of heterogeneity among communities. Most infected persons (81.5%) had counts less than 11 mf/20 mm3 of peripheral blood. Pruritus appeared much earlier in life while hydrocoele, limb and scrotal elephantiasis occurred much later in the population (> or = 40 years). Except in L. loa infections, mf-rate and mean mf-density increased with advancing host age (r = 0.713, P < 0.01). Fishermen, nomads and farmers had significantly higher infection rates (P < 0.05) than other occupational categories. Suggestions on the disease intervention involving treatment, prevention and vector control are highlighted.

In a study to assess the status of filariasis in the Jarawa River Valley of the savanna area of Nigeria, 940 self-selected residents from 10 villages were examined between March 1984 and April 1987. Overall results showed 105 (11.2%) had microfilaraemia and/or clinical signs of filariasis. Sixty-four (6.8%) and 20 (2.1%) persons, respectively, were infected with Mansonella perstans and Loa loa microfilariae (mff). Four of the 28 villagers examined had Wuchereria bancrofti mff in their night blood samples whereas 17 (1.8%) of all residents surveyed had clinical filariasis mainly due to lympho-obstructive manifestations: hydrocele (n = 11, 64.7%); enlargement of the inguinal nodes (n = 8, 47.1%) and elephantiasis (n = 2, 11.8%).