Estimation of the minimum number of leishmania major amastigotes required for infecting phlebotomus duboscqi (diptera: psychodidae)

Background. Leishmaniasis is a vector-borne disease in which Leishmania parasites are transmittedby the bite of phlebotomine sand flies. Amastigotes are ingested by the sand fly vector with ablood meal taken from an infected host. This is followed by their differentiation into metacyclicpromastigotes which are selectively released and permitted to migrate interiorly so as to makethem available for transmission by bite. However, the actual number of amastigotes ingested bythe sand fly in the blood meal is not known.Objective: Toinvestigate the minimum number of Leishmania major amastigotes required to causean infection in Phlebotomus duboscqi following an infective blood meal.Design: A laboratory based study.Setting: Centre for Biotechnology Research and Development, Kenya Medical Research institute, Nairobi.Results: Dissection of all fed sand flies at six days post-infective blood meal revealed that bloodcontaining one amastigote per 0.3µl in a total volume of 0.5ml was able to cause an infection in thesand flies, but very few sand flies got infected (7.6% and 9.6% respectively). Concentrations of tenamastigotes per 0.3µl in 0.5ml gave infection rates of 35.4% and 26.3% respectively, suggesting thateven when the concentration of amastigotes in a bloodmeal was high, not all sand flies feeding onit were able to pick up the parasites.Conclusions:These observations suggests that one amastigote is sufficient to cause an infection toa sand fly and as a result of multiplication in the gut and the existence of mechanisms that increasethe number of infective bites delivered by a female sand fly they are able to sustain the transmissionof leishmaniasis in an area

Comparison of Giemsa and acridine orange stains for the diagnosis of Leishmania donovani in biopsies of infected hamsters

Identical impression smears of spleen; liver and bone marrow biopsy materials from Leishmania donovani-infected hamsters were stained using either acridine orange or Giemsa. Spleen parasite-loads calculated from the two stains for identical biopsy material were significantly different from each other. However; liver and bone marrow parasite-loads calculated from either Giemsa-stained or acridine orange-stained biopsies were not significantly different from each other. This study has shown that acridine orange; which is a quick and simple technique; has great potential in the diagnosis of kala-azar when liver and bone marrow biopsies are used

Effects of anti-leishmania monoclonal antibodies on the development of leishmania major in phlebotomus duboscqi (diptera: psychodidae)

Background. Research in our laboratory has previously shown that immune-mediated transmission blocking may be applied to Leishmania infections and that the LPG molecule and anti-LPG monoclonal antibodies was found to be an excellent candidate against L. major infections. Objective: To test the effect of monoclonal antibodies (MABs) raised against different species ofLeishmania for their ability to inhibit development of Leishmania major in Phlebotomus duboscqi sand flies. Design: A laboratory based study. Setting: Centre for Biotechnology Research and Development; Kenya Medical Research Institute; Nairobi. Results: Sand fly dissections on days two; four and six post-feeding showed that monoclonal antibodies against L. donovani (Ld2cb and Ld3A3) were the most effective at inhibiting L. major development than those raised against L. aethiopica; L. major or L. tropica. Ld2cb inhibited L. major development by 82