The mechanical transmission of hepatitis B virus by the common bedbug (Cimex lectularius L.) in South Africa

Tests for both hepatitis B surface antigen (HBsAg) and hepatitis e antigen (HBeAg) were carried out on wild-caught and laboratory-colonized bedbugs (Cimex lectularius L.), the latter after hepatitis B virus (HBV)-positive blood-meals. Positivity for both antigens was interpreted as an indication of HBV infectivity. Of 22 pools in which were tested 211 bugs collected in the northern Transvaal, 18 were HBsAg-positive and 17 HBeAg-positive, with estimated infection rates of 156,7 and 137.7 per 1000 bugs respectively. Passage of HBV in bugs, allowing an extrinsic incubation period of 57-69 days, resulted in 19 out of 25 bugs being positive for HBsAg after the first passage; only a small number of these were positive for HBeAg. After the second passage all bugs tested were HBsAg-negative, showing that the virus had disappeared. Tests on the salivary glands and carcass of each bug at intervals up to 31 days after an infective meal showed a positivity rate of 98% (HBsAg) and 17% (HBeAg) for carcasses and 20% (HBsAg) and 0% (HBeAg) for salivary glands. Attempts to detect HBV particles in the salivary glands by electron microscopy failed. Bugs were shown to continue to excrete HBsAg in their faeces up to the 42nd day, and both HBsAg and HBeAg together up to the 30th day. HBsAg particles were only detected by electron microscopy in faeces hal1lested on the 10th day. The results as a whole· indicate that no biological mUltiplication of virus occurs in C. lectularius but that mechanical transmission from inseCts to man could occur by: (i) contamination of a person when crushing infective bugs; (ii) contamination from infected faeces; and (iii) infection by bite due to regurgitation or interrupted feeding

Attempts to transmit hepatitis B virus to chimpanzees by arthropods

Bedbugs (Cimex lectularius L.) were fed on an infective blood-hepatitis B virus (HBV) mixture. Further bedbugs and tampan ticks (Ornithodoros moubata [MurrayJ) were fed on HBV-carrier chimpanzees. After a 10 - 13 day interval for oviposition, tests done on samples of individual arthropods showed that 53 - 85% of the bugs were HBsAg-positive and none HBeAg-positive, while 100% of the ticks were HBsAgpositive and 88% HBeAg-positive. The remaining arthropods were fed on 3 susceptible chimpanzees, which had failed to develop HBV infection after 11 months, indicating no transmission had occurred. Subsequently the presence of viable virus in the original infective meals was confirmed by inoculation of the relevant donor sera directly into the 3 still susceptible chimpanzees. HBV infections quickly followed in each animal. It is concluded that, while mechanical transmission of HBV is most unlikely after a 10 - 13-day interval between feedings in bedbugs and tampans, it is still possible that mechanical transmission between humans might occur during interrupted feeds

Une enquete des Faunes de Moustiques et de Culicoides dans deux localites de la region du Karoo en Afrique du Sud avec certaines observations Ecologiques

The mosquito and Culicoides faunas were surveyed at Bethulie and Luckhoff in the arid Karoo region, southern Orange Free State, to determine which species occurred, their relative prevalence and the effects of rainfall. The feeding preferences of these insects were also investigated by means of baited catches. Twenty-three mosquito species and 16 Culicoides species were collected. The commonest mosquito species, with their feeding preferences, if known, were as follows: Culex (Culex) univittatus Theo and Culex (Culex) pipiens Linnaeus, which are strongly ornithophilic and poorly anthropophilic; Culex (Culex) theileriTheo, which feeds on sheep and man avidly but is only moderately ornithophilic; Aedes (Neomelaniconion) luridus McIntosh, Aedes (Neomelaniconion) lineatopennis (Ludlow), Aedes (Ochlerotatus) caballus (Theo) and Aedes (Ochlerotatus) juppi McIntosh, all of which feed on sheep and man readily and which can aestivate as eggs for up to 20 months but only appear in numbers after rain; Anopheles (Cellia) listeri De Meillon, Anopheles (Cellia) squamosus Theo, Culex (Culex) quinquefasciatus Say and Culiseta (Allotheobaldia) longiareolata (Macquart). By far the commonest Culicoides at both localities was Culicoides pycnostictus Ingram & Macfie, which is strongly ornithophilic and also feeds on sheep. The following 5 species were also prevalent: Culicoides similis Carter,Ingram & Macfie, Culicoides spec. nov. 1., Culicoides schultzei (Enderlein), Culicoides ondersteportensis Fiedler and Culicoides nivosus De Meillon. The last species is strongly ornithophilic.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Evolutionary history of a mosquito endosymbiont revealed through mitochondrial hitchhiking

Due to cytoplasmic inheritance, spread of maternally inherited Wolbachia symbionts can result in reduction of mitochondrial variation in populations. We examined sequence diversity of the mitochondrial NADH dehydrogenase subunit 4 (ND4) gene in Wolbachia-infected (South Africa (SA), California and Thailand) and uninfected (SA) Culex pipiens complex populations. In total, we identified 12 haplotypes (A–L). In infected populations, 99% of individuals had haplotype K. In the uninfected SA population, 11 haplotypes were present, including K. Nuclear allozyme diversity was similar between infected and uninfected SA populations. Analysis of nuclear DNA sequences suggested that haplotype K presence in uninfected SA Cx. pipiens was probably due to a shared ancestral polymorphism rather than hybrid introgression. These data indicate that Wolbachia spread has resulted in drastic reduction of mitochondrial variability in widely separated Cx. pipiens complex populations. In contrast, the uninfected SA population is probably a cryptic species where Wolbachia introgression has been prevented by reproductive isolation, maintaining ancestral levels of mitochondrial diversity. Molecular clock analyses suggest that the Wolbachia sweep occurred within the last 47 000 years. The effect of Wolbachia on mitochondrial dynamics can provide insight on the potential for Wolbachia to spread transgenes into mosquito populations to control vector-borne diseases