Genetic homogeneity within Leishmania (L.) infantum isolated from human and dogs: the relationship with the sandfly fauna distribution in endemic areas of Nueva Esparta State, Venezuela.

Leishmania infantum has been described as a highly polymorphic group of parasites, responsible for visceral leishmaniasis and cutaneous leishmaniasis. In this paper we report the life-cycle of L. (L.) infantum in an endemic area of visceral leishmaniasis in Venezuela, by using molecular diagnosis and characterization of parasites isolated from dogs, humans with visceral leishmaniasis and sand flies. The molecular characterization was carried out by use of kDNA restriction analysis, dot-blot hybridization with species-specific probes and RFLP of the PCR products. The results demonstrated that L. (L.) infantum is the parasite responsible for VL in the island. The parasites were revealed to be genetically homogeneous with no intra-specific differences between isolates from different individuals. The highest homology of the isolates was with L. (L.) infantum from the Old World rather than with L. (L.) chagasi from the New World. Additionally, we report the geographical distribution of Lutzomyia longipalpis, and the relationship with the transmission of L. (L.) infantum in the studied area.

Canine visceral leishmaniasis on Margarita Island (Nueva Esparta, Venezuela).

The frequency of American visceral leishmaniasis affecting humans on Margarita Island, Venezuela, has increased in recent years, and infected dogs appear to constitute the principal source of infection. ELISA tests with Leishmania donovani promastigotes and rK39 antigen from L. chagasi in serum from 541 dogs were positive in 33.1% and 21.6% of the samples, respectively. A second blood sample taken from 50 animals after 8-10 months revealed an increase from 24% to 40% of ELISA positivity to both antigens, suggesting high susceptibility and transmission in the canine population. Among 42 serologically positive dogs, 33% of which showed clinical signs of disease, 79% were positive in polymerase chain reactions using primers specific for the L. donovani complex. Control measures including epidemiological hypersurveillance, the humane sacrifice of infected dogs, and rapid diagnosis and treatment of human cases have been initiated.

Epidemiologic aspects of American visceral leishmaniasis in an endemic focus in Eastern Venezuela.

An endemic focus of American visceral leishmaniasis (AVL) in eastern Venezuela has been evaluated in terms of patients (n = 48), immunologic reactivity to Leishmania in household contacts (n = 187) and neighborhood controls (n = 170), detection of Leishmania (L. donovani complex) in dogs and wild animals by the polymerase chain reaction (PCR) and characteristics of the sandfly population. The male:female ratio of patients was 1.18:1; 89.6% were < or =12 years old. Serologic reactivity was significantly higher in household contacts than in controls (P = 0.0008), as was the size of leishmanin reactions in contacts < or =10 years of age (P = 0.0141). Leishmania donovani complex-specific PCRs were positive in dogs, an opossum (Didelphis marsupialis), and a black rat (Rattus rattus). Lutzomyia longipalpis and Lu. evansi, both implicated in the transmission of AVL, were identified among the 386 sand flies examined. These observations provide the bases for an active control program as well as further studies of reservoirs and vector-host relationships in this area.

Possible relationship between allergic disease and infection by Giardia lamblia.

In order to better understand the possible relationship between allergic reactivity and infection with G. lamblia, specific IgE responses and skin test reactivity were evaluated in allergic or nonallergic Venezuelan children, with or without G. lamblia infection. Two groups of children were studied: one from our Allergy Clinic and the other from a slum area of Caracas. The total serum IgE levels in children from the slum area were significantly higher in those with intestinal helminthic parasites and giardiasis, compared with those with helminthiasis only (P < .001). In atopic children with giardiasis we also found an enhanced IgE antibody response to common environmental allergens (P < .05). As G. lamblia produces intestinal mucosal damage, we also studied the reactivity to cow milk and found that 22% of the children belonging to the low socioeconomic level demonstrated the presence of significant levels of specific IgE against this antigen. Of these milk-positive subjects, 40% were infected by G. lamblia in contrast to only 21% of the milk-negative children (P < .05). These results suggest that children with giardiasis may be exposed to greater amounts of intestinally absorbed antigens. We also studied the specific allergic response to G. lamblia, and found that in an unselected group of children of low socioeconomic level, 25% had positive skin tests, as did 50% of persons with symptomatic giardiasis. The presence of serum anti-Giardia IgE was also demonstrated in 22% of patients with giardiasis.