ABSTRACT
Background. South eastern parts of Iran remain endemic for malaria infection. There is some concern that malaria infection may spread into Bushehr, which is located in the south western part bordering the Persian Gulf and at the periphery of the declared endemic region Hormozgan province due to frequency of visitors from eastern endemic areas and from neighboring malaria endemic countries. We investigated malaria prevalence in Bushehr. Methods and Results. Attempts were made to identify malaria active infection in blood smears and malaria specific antibody and antigens in serum samples. Traditional blood smears prepared from 1955 blood specimens yielded no definitive malaria positive case by microscopic technique. A total of 270 (13.8%) serum samples were positive for malaria antibodies. Using specific ELISA kits, presence of histidine rich proteins and lactate dehydrogenase antigens were investigated in serum samples. No histidine rich proteins specific for P. falciparum were detected amongst 270 antibody positive samples. However, six samples representing 0.3% of total population, were found to be positive for plasmodium pan specific lactate dehydrogenase antigens. This suggested the possibility of low level exposure to malaria in Bushehr community. Conclusions. Out of a total of 1955 samples tested, 270 (13.8%) were positive for malaria antibodies and six (0.3%) of these were positive for plasmodium-specific lactate dehydrogenase antigen suggesting a low level exposure to malaria in a hypoendemic region based on immunological testing. Since none of the 270 antibody samples were positive for histidine rich protein antigens, there is scope for further testing of blood samples by molecular methods such as polymerase chain reactions to confirm the plasmodium species and provide information valuable for future investigations. Our testing strategy for hypoemdemic malaria can be used as a template for investing malaria in 32 eliminating countries for testing ongoing transmission. This approach may be useful as a method in epidemiological studies.
ABSTRACT
Dogs which are infected with leishmania parasites serve as major reservoir hosts for zoonotic visceral leishmaniasis. The incidence of zoonotic visceral leishmaniasis is rising in many countries. This may be associated with the continuing drift of people and their pets from rural areas into peri-urban settings, particularly at the fringe of large cities. At the same time, there is evidence of adaptation of sand fly vectors to these urban settings. This has created an alarming situation because, even though domestic and stray dogs may be infected, many remain asymptomatic but are still highly infectious to the sand fly vectors and thus pose a serious threat to human health. Over half of the infected dogs have asymptomatic infections and current assays are not sensitive enough under field conditions to distinguish asymptomatic from symptomatic dogs. There is an urgent need for a specific and sensitive screening tool for use in the field. We have previously demonstrated that promastigote exo-antigen-based ELISAs can be used in the specific diagnosis of human visceral leishmaniasis (HVL). A cocktail of exo-antigens prepared from three species (L. infantum, L. donovani, and L. major) was used to develop and optimize a canine ELISA assay. Serum samples from dogs with a variety of pathological conditions but living in a non-leishmania endemic area were used as negative controls and their reactivity was used to determine a cut-off value for the ELISA. Samples from dogs residing in a leishmania endemic area were tested in parallel using direct agglutination (DAT), immunofluorescence (IFAT), and ELISA. The ELISA results correlated closely (100%) with the clinical symptoms, and were elevated in one asymptomatic dog. This sample was also found to be positive by IFAT. Based on its sensitivity and specificity, the cocktail exo-antigen-based ELISA may prove useful, even at 1:2,000 serum dilutions, for screening dogs in different geographical regions of the world.
