Is there a risk of filarial infection during long-term missions in Haiti?

BACKGROUND: Haiti has the highest prevalence of lymphatic filariasis (Wuchereria bancrofti) in the Western Hemisphere. Still, the risk of filarial infection for long-term visitors such as humanitarian aid workers or military personnel is uncertain. The presented study analyzed the exposure to W. bancrofti in Chilean participants of the UN Stabilization Mission in Haiti (MINUSTAH) in 2011. METHODS: Blood samples collected from 531 participants were screened for antifilarial antibodies by IgG ELISA, and, if positive, analyzed by immunofluorescence assay (IFA), IgG4 ELISA, Real-Time PCR, and circulating filarial antigen (CFA) card test. RESULTS: ELISA screening was positive in 10 cases. Seroconversion occurred in only two cases (0.38%) based on ELISA values determined in samples taken before and after deployment. Positive IgG ELISA values could not be confirmed by IFA and IgG4 ELISA. Real-Time PCR and CFA testing did not reveal the presence of filaria. CONCLUSIONS: Our data indicate that in the examined cohort of MINUSTAH participants in 2011, the risk of filarial exposure or infection was low.

Testicular swelling due to lymphatic filariasis after brief travel to Haiti.

After 6 months of a trip to Haiti, a 25-year-old healthy man presented with a 6-week history of a very slow progressive intermittent bilateral testicular pain and swelling. The biopsies in both testicles revealed the presence of a dead filarial parasite. Polymerase chain reaction products of the DNA from the biopsy were shown to have a 100% identity to Wuchereria bancrofti. Despite being uncommon in travelers, this presentation of W. bancrofti highlights the possibility of acquiring W. bancrofti during short-term trips to highly endemic regions of the world (i.e., Haiti).

Lymphatic filariasis in Brazil: epidemiological situation and outlook for elimination.

Since the World Health Assembly's (Resolution WHA 50.29, 1997) call for the elimination of lymphatic filariasis by the year 2020, most of the endemic countries identified have established programmes to meet this objective. In 1997, a National Lymphatic Filariasis Elimination Plan was drawn up by the Ministry of Health of Brazil, creating local programs for the elimination of Bancroftian filariasis in areas with active transmission. Based on a comprehensive bibliographic search for available studies and reports of filariasis epidemiology in Brazil, current status of this parasitic infection and the outlook for its elimination in the country were analysed. From 1951 to 1958 a nationwide epidemiological study conducted in Brazil confirmed autochthonous transmission of Bancroftian filariasis in 11 cities of the country. Control measures led to a decline in parasite rates, and in the 1980s only the cities of Belém in the Amazonian region (Northern region) and Recife (Northeastern region) were considered to be endemic. In the 1990s, foci of active transmission of LF were also described in the cities of Maceió, Olinda, Jaboatão dos Guararapes, and Paulista, all in the Northeastern coast of Brazil. Data provide evidence for the absence of microfilaremic subjects and infected mosquitoes in Belém, Salvador and Maceió in the past few years, attesting to the effectiveness of the measures adopted in these cities. Currently, lymphatic filariasis is a public health problem in Brazil only in four cities of the metropolitan Recife region (Northeastern coast). Efforts are being concentrated in these areas, with a view to eliminating the disease in the country.

Does longevity of adult Wuchereria bancrofti increase with decreasing intensity of parasite transmission? Insights from clinical observations.

To interrupt transmission of Wuchereria bancrofti, a parasite that causes lymphatic filariasis, mass treatment of at-risk populations with antifilarial drugs is recommended for 4-6 years, the minimum estimated adult worm lifespan. Factors associated with adult worm longevity are unknown. In Recife, Brazil, we conducted a retrospective cohort study of 57 men whose adult W. bancrofti were not sensitive to diethylcarbamazine and who were followed with semi-annual physical examinations (to detect intrascrotal nodules, indicative of adult worm death) and ultrasound examinations (to detect the 'filaria dance sign' (FDS), indicative of living adult worms). After 5 years, the FDS remained detectable in 10 (24.4%) of 41 adult worm nests in 25 men from areas of high filariasis transmission intensity and in 30 (90.9%) of 33 nests in 32 men from areas of low transmission (P<0.001). New nodules and adult worm nests were detected only in men from high-transmission areas. Of 30 men who were microfilaria-positive initially and whose FDS remained detectable after 5 years of follow-up, 19 (63.3%) remained microfilaria-positive in 5 ml blood (mean density, 0.4 per ml). In conclusion, survival of adult W. bancrofti is inversely associated with transmission intensity. These findings have implications for filariasis elimination and research.

The histopathology of bancroftian filariasis revisited: the role of the adult worm in the lymphatic-vessel disease.

Although morphology is generally limited to static images, the histopathological features of bancroftian lymphatic disease are presented here in a way that is as dynamic as possible and closely associated with the clinical, ultrasonographic and surgical characteristics. The protean spectrum of alterations seen in the host's lymphatic vessels is discussed, and the changes caused by the live and dead worms are highlighted, as independent events. Evidence of a remodelling process, in which the lymphatic endothelial cells appear to have a key role, is provided for the first time. Despite many new pieces of information, there remain many 'blank pages' in the natural history of bancroftian filariasis.

Fine structure of intrascrotal lymphatic vessels infected by Wuchereria bancrofti adult worms.

Lymphangiectasia represents a basic phenomenon of acute and chronic pathology in lymphatic filariasis, and the prevalence or degree of lymphatic dilation caused by filarial worms is considered an indirect measurement of the altered lymphatic function. We examined the morphological alterations of intrascrotal lymphatic vessels surgically removed from a volunteer infected by adult worms of Wuchereria bancrofti. Scanning electron microscopy revealed lymphatic vessels with an irregular endothelium and adherent flattened lymphocytes and macrophages in variable proportions. On transmission electron microscopy the lymphatic vessels showed a thin endothelium which had an irregular contour and projected several cytoplasmic processes into the lumen. Numerous micropinocytotic vesicles and collagen fibers were abundant and disorganized. The hyperplastic endothelial cells and the subendothelial fibrosis suggest that abnormal changes in these cells may play a crucial role in the development of lymphangiectasia.

Bancroftian filariasis in Maceio, state of Alagoas, Brazil: Observations on Culex quinquefasciatus after blood feeding on individuals with different densities of microfilariae in the peripheral blood stream.

Females of laboratory-reared Culex quinquefasciatus were allowed to take blood meals on individuals with low (1-100 microfilariae/ml of peripheral blood), moderate (101-500 microfilariae/ml), and high (> 500 microfilariae/ml) microfilaremia. The mosquitoes ingested 1.39-3.80 microl of blood and infective third-stage (L3) larvae were first recorded 13-14 days after the infecting blood meal. The number of microfilariae ingested by mosquitoes was proportional to the density of microfilariae in the peripheral blood of the human subjects, but with a concentration factor of up to 6.5 times the expected number. Survival of mosquitoes was not influenced by the density of microfilariae in the peripheral blood of infected individuals. Infectivity indices were proportional to microfilaremia in human subjects. The number of L3 larvae/female (intensity of infection) was not influenced by individual microfilaremia. The highest vector efficiency and the best experimental infection index were recorded in mosquitoes that blood fed on individuals with moderate microfilaremia. The results are discussed in relation to the transmission on Bancroftian filariasis in the study area.

The LYMFASIM simulation program for modeling lymphatic filariasis and its control.

The LYMFASIM modeling framework for the transmission and control of the tropical parasitic disease lymphatic filariasis is described and its use in the context of an endemic community in north-eastern Brazil is illustrated. Lymphatic filariasis is a disease with a complex natural history with many unknowns. This complicates decision making with respect to control strategies. With LYMFASIM, a variety of hypotheses can be tested about the life history of the parasite Wuchereria bancrofti, its transmission from man to man through mosquitoes, the role of the immune system in regulating parasite numbers, the development of disease symptoms, and the effects of control measures (drug treatment or mosquito control). The implications of alternative assumptions and uncertainty about the quantification of parameters for the effectiveness of control strategies can be investigated. Thanks to the use of stochastic microsimulation, LYMFASIM is highly flexible and can be adapted and extended as new knowledge emerges.

Transplacental transmission of Wuchereria bancrofti in Haitian women.

To document the occurrence of transplacental transmission of microfilariae and to determine how frequently it occurred, umbilical cord blood samples and placental tissues were collected from 22 microfilaria-positive women in an area with endemic Wuchereria bancrofti. Microfilaria (mf) counts in the women ranged from 1 to 3,820 mf/ml. Microfilariae were detected in 2 placenta samples and a single cord blood sample. The positive cord blood sample and 1 of the positive placenta samples came from the same woman; no microfilariae were found in a finger prick sample taken from the infant 3 wk after delivery. Our results suggest that microfilariae cross the placenta in less than 10% of pregnancies of microfilaria-positive mothers. Furthermore, the microfilaria count of the mother does not seem to influence directly whether microfilariae are present in the placental blood pool. Although actual transfer of microfilariae to the fetus may occur infrequently, exposure to parasite antigens occurs with much greater frequency. The effect of in utero exposure to either microfilariae or parasite antigens may render newborns tolerant and explain why children born to infected mothers are almost 3 times more likely to become infected than are children born to uninfected women.

In vitro differentiation of Wuchereria bancrofti (Filariidae)

Wuchereria bancrofti microfilariae were isolated from blood of infected individuals and cultured in vitro under several conditions. RPMI 1640 and TC-199 media supplemented with fetal or human serum were able to support the microfilariae for periods up to 35 days at 37-C (viability > 85%). In contrast, in minimal essential medium the microfilariae did not survive for more than 48h. In culture kept at 28-C, where viability was much lower (approximately 10% on day 15), microfilariae differentiated into type IV larvae ("sausage form). The in vitro maintainance of microfilarial larval forms is particularly important in the case of W. bancrofti due to the absence of an experimental model for the disease

[Lymphatic filariasis in Haiti. Results of treatment with diethylcarbamazine in the town of Limbe]. / Filariose lymphatique en Haiti. Résultats du traitement par le diéthylcarbamazine dans la ville du Limbe.

In the town of Limbe, in Haiti, 16,8% of the inhabitants show W. bancrofti microfilariae in their blood taken by finger prick between 8.00 and 10.00 p.m. From those positive patients, 208 have received a cure of DEC at the dosage of 6 mg/kg/day during ten days. The control of the therapeutic efficacity among 190 patients, after three and a half months of this cure, shows a negativity of 72%. The positives patients show a very low parasitic charge (MfD50 = 1.9). If the secondary effects are frequent (83.7%), they are often benign and temporary.