Anopheline mosquitoes and their role for malaria transmission in an endemic area, southern Iran

A comparative laboratory diagnosis of malaria: microscopy versus rapid diagnostic test kits

OBJECTIVE

To compare the two methods of rapid diagnostic tests (RDTs) and microscopy in the diagnosis of malaria.

METHODS

RDTs and microscopy were carried out to diagnose malaria. Percentage malaria parasitaemia was calculated on thin films and all non-acute cases of plasmodiasis with less than 0.001% malaria parasitaemia were regarded as negative. Results were simply presented as percentage positive of the total number of patients under study. The results of RDTs were compared to those of microscopy while those of RDTs based on antigen were compared to those of RDTs based on antibody. Patients' follow-up was made for all cases.

RESULTS

All the 200 patients under present study tested positive to RDTs based on malaria antibodies (serum) method (100%). 128 out of 200 tested positive to RDTs based on malaria antigen (whole blood) method (64%), while 118 out of 200 patients under present study tested positive to visual microscopy of Lieshman and diluted Giemsa (59%). All patients that tested positive to microscopy also tested positive to RDTs based on antigen. All patients on the second day of follow-up were non-febrile and had antimalaria drugs.

CONCLUSIONS

We conclude based on the present study that the RDTs based on malaria antigen (whole blood) method is as specific as the traditional microscopy and even appears more sensitive than microscopy. The RDTs based on antibody (serum) method is unspecific thus it should not be encouraged. It is most likely that Africa being an endemic region, formation of certain levels of malaria antibody may not be uncommon. The present study also supports the opinion that a good number of febrile cases is not due to malaria. We support WHO's report on cost effectiveness of RDTs but, recommend that only the antigen based method should possibly, be adopted in Africa and other malaria endemic regions of the world.

Preferential feeding success of laboratory reared Anopheles stephensi mosquitoes according to ABO blood group status

Recent epidemiological evidences revealed a higher rate of O blood group in the residents of malaria-endemic areas suggesting that groups A, B, and AB associated with a higher disease severity and fatality. Also recent data showed the low prevalence of AB group within the malaria-endemic residents in south of Iran and India. The aim of this study was to determine the ABO blood groups preference of Anopheles stephensi which is the main malaria vector in Iran, southwest Asia, and India. An. stephensi mosquitoes were fed either artificially on A/B/O/AB membrane blood feeders or directly on human volunteer hands and forearms of A/B/O/AB groups in a cage under lab conditions. Phenotype and genotype analyzes of 450-blood-fed mosquito specimens using agglutination and multiplex-allele-specific PCR revealed a significant blood preference of An. stephensi to AB group (40%) than other groups of A (24%), B (21%), and O (15%) in combination of both experiments. High preference of An. stephensi to AB group might increase malaria infection and fatality in this blood group and resulted in low frequency of AB group in the residents of malaria endemic areas. The data suggested that malaria vectors, like parasites may have selection pressure on human genotypes.

Some ecological attributes of malarial vector Anopheles superpictus Grassi in endemic foci in southeastern Iran

OBJECTIVE

To determine the bionomics and susceptibility status of the malarial vector Anopheles superpictus (An. superpictus) to different insecticides in the Sistan-Baluchestan province which has the highest malarial prevalence in Iran.

METHODS

Different sampling methods, in addition to scoring abdominal conditions, were used to define the seasonal activity and endo/exophilic behavior of this species. In addition, the standard WHO susceptibility tests were applied on adult field strains.

RESULTS

Most adult mosquitoes were collected from outdoor shelters. The peak of seasonal activity of An. superpictus occurred at the end of autumn. Most larvae were collected from natural and permanent breeding places with full sunlight and no vegetation. Blood feeding activities occurred around midnight. Compared with the abdominal conditions of adult mosquitoes collected indoors, the abdominal conditions of adult mosquitoes collected outdoors were gravid and semigravid. This species was suspected to be resistant to DDT, but was susceptible to other insecticides.

CONCLUSIONS

An. superpictus was present in almost all outdoor shelters, and the ratios of gravid, semigravid/unfed, and freshly fed confirmed that this species had a higher tendency to rest outdoors than indoors. This behavior can protect An. superpictus from indoor residual spraying in this malarious area. To the best of our knowledge, this is the first report on the susceptibility status of An. superpictus in Southeastern Iran. We do not suggest the use of DDT for indoor residual spraying in southeast Iran.

ABO blood groups of residents and the ABO host choice of malaria vectors in southern Iran

Recent epidemiological evidences revealed the higher prevalence of 'O' blood group in the residents of malaria-endemic areas. Also some data indicated preference of mosquitoes to 'O' group. The aim of this study was to determine ABO group ratio in the residents as well as ABO group preference of Anopheles in two malaria endemic areas in south of Iran. Agglutination method was used for ABO typing of residents. Field blood fed Anopheles specimens were tested against vertebrate DNA using mtDNA-cytB PCR-RFLP and then the human fed specimens were tested for ABO groups using multiplex allele-specific PCR. A total of 409 human blood samples were identified, of which 150(36.7%) were 'O' group followed by 113(27.6%), 109(26.7%), and 37(9.0%) of A, B, and AB groups respectively. Analyzing of 95 blood fed mosquitoes revealed that only four Anopheles stephensi had fed human blood with A(1), B(1), and AB(2) groups. Result of this study revealed high prevalence of O group in south of Iran. To our knowledge, it is the first ABO molecular typing of blood meal in mosquitoes; however, due to low number of human blood fed specimens, ABO host choice of the mosquitoes remains unknown. This study revealed that ABO blood preference of malaria vectors and other arthropod vectors deserves future research.

Resolution pattern of jaundice among children presenting with severe malaria in rural South-West Nigeria

OBJECTIVE

To compare the pattern of jaundice resolution among children with severe malaria treated with quinine and artemether.

METHODS

Thirty two children who fulfilled the inclusion criteria were recruited for the study from two hospitals with intensive care facilities. They were divided into two groups; 'Q' and 'A', receiving quinine and artemether, respectively. Jaundice was assessed by clinical examination.

RESULTS

Sixteen out of 32 children recruited (representing 50%) presented with jaundice on the day of recruitment. The mean age was (7.00°C2.56) years. On day 3, four patients in 'A' and six patients in 'Q' had jaundice. By day 7, no child had jaundice.

CONCLUSION

The study has shown that both drugs resolve jaundice although artemether relatively resolves it faster by the third day.

Irritability of malaria vector, Anopheles sacharovi to different insecticides in a malaria-prone area

OBJECTIVE

To determine the susceptibility and irritability level of malaria vector Anopheles sacharovi (An. sachrovi) to different insecticides in a malaria-prone area.

METHODS

Susceptibility and irritability levels of field collected strain of An. sacharovi to WHO standard papers of DDT 4%, dieldrin 0.4%, malathion 5%, fenitrothion 1%, permethrin 0.75%, and deltamethrin 0.05% were determined in East Azerbaijan of Iran during reemerging of malaria as described by WHO.

RESULTS

Results showed that at the diagnostic dose of insecticides this species exhibited resistance to DDT, tolerant to dieldrin and but somehow susceptible to fenitrothion, malathion, permethrin and deltamethrin. The results of irritability of this species to DDT, lambdacyhalothrin, permethrin cyfluthrin and deltamethrin revealed that DDT had had the most and deltamethrin the least irritancy effect. The average number of take offs/fly/minutes for DDT was 0.8±0.2. The order of irritability for permethrin, lambdacyhalothrin, cyfluthrin and deltamethrin were 0.7±0.2, 0.5±0.2, 0.5±0.3, and 0.2±0.1, respectively.

CONCLUSIONS

Results of this study reveals the responsiveness of the main malaria vector to different insecticides. This phenomenon is depending on several factors such as type and background of insecticide used previously, insecticide properties, and physiology of the species. Careful monitoring of insecticide resistance and irritability level of species could provide a clue for appropriate selection of insecticide for malaria control.