Plasmodium berghei ANKA: selection of resistance to piperaquine and lumefantrine in a mouse model.

We have selected piperaquine (PQ) and lumefantrine (LM) resistant Plasmodium berghei ANKA parasite lines in mice by drug pressure. Effective doses that reduce parasitaemia by 90% (ED(90)) of PQ and LM against the parent line were 3.52 and 3.93 mg/kg, respectively. After drug pressure (more than 27 passages), the selected parasite lines had PQ and LM resistance indexes (I(90)) [ED(90) of resistant line/ED(90) of parent line] of 68.86 and 63.55, respectively. After growing them in the absence of drug for 10 passages and cryo-preserving them at -80 degrees C for at least 2 months, the resistance phenotypes remained stable. Cross-resistance studies showed that the PQ-resistant line was highly resistant to LM, while the LM-resistant line remained sensitive to PQ. Thus, if the mechanism of resistance is similar in P. berghei and Plasmodium falciparum, the use of LM (as part of Coartem) should not select for PQ resistance.

National scale-up of HIV testing and provision of HIV care to tuberculosis patients in Kenya.

SETTING: Kenya, one of the 22 tuberculosis (TB) high-burden countries, whose TB burden is fuelled by the human immunodeficiency virus (HIV). OBJECTIVE: To monitor and evaluate the implementation of HIV testing and provision of HIV care to TB patients in Kenya through the establishment of a routine TB-HIV integrated surveillance system. DESIGN: A descriptive report of the status of implementation of HIV testing and provision of HIV interventions to TB patients one year after the introduction of the revised TB case recording and reporting system. RESULTS: From July 2005 to June 2006, 88% of 112835 TB patients were reported to the National Leprosy and TB Control Programme, 98773 (87.9%) of whom were reported using a revised recording and reporting system that included TB-HIV indicators. HIV testing of TB patients increased from 31.5% at the beginning of this period to 59% at the end. Of the 46428 patients tested for HIV, 25558 (55%) were found to be HIV-positive, 85% of whom were provided with cotrimoxazole preventive treatment and 28% with antiretroviral treatment. CONCLUSION: A country-wide integrated TB-HIV surveillance system in TB patients can be implemented and provides essential data to monitor and evaluate TB-HIV related interventions.

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 transmitted by the bite of phlebotomine sand flies. Amastigotes are ingested by the sand fly vector with a blood meal taken from an infected host. This is followed by their differentiation into metacyclic promastigotes which are selectively released and permitted to migrate interiorly so as to make them available for transmission by bite. However, the actual number of amastigotes ingested by the sand fly in the blood meal is not known. OBJECTIVE: To investigate the minimum number of Leishmania major amastigotes required to cause an 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 blood containing one amastigote per 0.3 microl in a total volume of 0.5 ml was able to cause an infection in the sand flies, but very few sand flies got infected (7.6% and 9.6% respectively). Concentrations of ten amastigotes per 0.3 microl in 0.5 ml gave infection rates of 35.4% and 26.3% respectively, suggesting that even when the concentration of amastigotes in a bloodmeal was high, not all sand flies feeding on it were able to pick up the parasites. CONCLUSIONS: These observations suggests that one amastigote is sufficient to cause an infection to a sand fly and as a result of multiplication in the gut and the existence of mechanisms that increase the number of infective bites delivered by a female sand fly they are able to sustain the transmission of leishmaniasis in an area.

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 of Leishmania 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% in sand flies fed on 1 x 10(6) amastigotes while Ld3A3 inhibited by 72%; 58% and 74% in those fed on 1 x 10(5) amastigotes respectively. Monoclonal antibodies against L. aethiopica (Lae 3c6) inhibited L. major development by 28% and 40% for sand flies fed on 1 x 10(6) and 1 x 10(5) amastigotes respectively. Anti-L. major monoclonal antibody (Lm5A5) inhibited L. major development by 16% in sand flies fed on 1 x 10(6) amastigotes and 25% in sand flies fed on 1 x 10(5) amastigotes. Anti-L. tropica antibody (Lt2c8) inhibited L. major development in P. duboscqi fed on 1 x 10(6) by 28 %and 33% in those fed on 1 x 10(5) amastigotes. Most of the parasites seen in sand flies which fed on L. donovani mABs (Ld2cb and Ld3A3) were nectomonads and a few haptomonads. In all the control groups, parasite development followed the normal developmental stages up to the metacyclic stage. In sand fly groups fed on monoclonal antibodies raised against L. aethiopica, L. major or L. tropica there was limited parasite development inhibition, and the promastigotes developed and migrated forward in a normal pattern as observed in the controls. CONCLUSIONS: These results suggests a possible role of humoral mechanisms in protection against leishmaniasis and potentially useful in reducing parasite development in the sand fly.

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