First isolation of West Nile virus in Zambia from mosquitoes

Mosquito surveillance studies to identify mosquito-borne flaviviruses have identified West Nile Virus (WNV) for the first time in Zambia. The Zambian WNV isolate from Culex quinquefasciatus mosquitoes collected in the Western Province was closely related genetically to WNV lineage 2 South African strains which have been previously shown to be highly neuroinvasive. These data provide the first evidence of the circulation of WNV in Zambia and suggest there should be an increased awareness of possible associated human and animal diseases in that country.

Sero-prevalence of Bovine Brucellosis and associated risk factors in mbeya region, Southern highlands of Tanzania

A cross-sectional study was conducted to establish the seroprevalence of brucellosis and associated risk factors in indigenous and exotic breeds of cattle from 178 farms in Mbeya region. A total of 1211 cattle (929exotic cattle from 108 commercial farms and 282 indigenous cattle from 70 traditional farms) were tested for Brucella antibodies using the Rose Bengal Plate Test (RBPT) and competitive Enzyme Linked Immunosorbent Assay (c-ELISA) as screening and confirmatory tests, respectively. The overall animal-level seroprevalence was 9.3%; 11.3% (95% CI: 9.4-13.5) in indigenous cattle and 2.8% (95% CI:1.4-5.6) in exotic cattle. Further, the overall herd level seroprevalence was 32.0%; 50.5% (95% CI: 40.9-59.9) in indigenous cattle and 4.2% (95% CI: 1.3-12.4) in exotic cattle. Infections were higher in cattle aged 6-10 years old, (39.8%; 95% CI: 31.2-49.1) followed by those aged 1-5 years (5.8%; 95% CI: 4.8-6.6) and 11-15years old (2.7%; 95% CI: 0.8-8). When compared to cattle sampled from herds size of 1-50, those sampled from the herd sizes of 51-100 and 101-150 had higher odds of brucellosis seropositivity [(OR=3.6, CI: 1.76-7.16, p<0.001) and (OR=3.0, CI: 1.09-8.04, p=0.033). The odds of seropositivity in animals which calved on pasture was 3.0 (CI: 1.1-7.8, p=0.028) compared to those that calved at home. Brucella seroprevalence was also observed to vary according to districts, with Mbarari district recording the highest (45.4%). It is evident from the study that Brucellosis is present in Mbarari, Mbeya and Momba districts of Mbeya Region. The findings of this study provide some baseline data that could contribute to the design and implementation of brucellosis control measures in the study areas.

First record of epizootic ulcerative syndrome from the Upper Congo catchment: An outbreak in the Bangweulu swamps, Zambia

We report on the first outbreak of epizootic ulcerative syndrome (EUS) amongst wild fish populations in the Bangweulu swamps, an inland delta, in the north of Zambia during 2014. The area supports a large and diverse fish fauna related to, but distinct from, that of the Zambezi River system where EUS outbreaks have occurred since 2006. A sizeable artisanal fishery, based on extensive fish weirs, is sustained by the annual flooding of the swamps, and observations of the disease outbreak by fishermen were recorded. Signs typical of infection with Aphanomyces invadans were observed in a number of species. Clinical observations, histology and molecular diagnostic methods were used to confirm infection with A. invadans in two of the most commonly and severely affected species. Several features of the wetland may have contributed to the outbreak and the annual recurrence of the disease. Modes by which the disease may have been introduced into the swamps are discussed. The outbreak is of great significance as the Bangweulu swamps drain into the Congo River in neighbouring Democratic Republic of Congo, Africa's largest drainage system with an extensive and diverse fish fauna previously unaffected by EUS.

Serological and PCR investigation of Yersinia pestis in potential reservoir hosts from a plague outbreak focus in Zambia

Background

Plague is a bacterial zoonotic disease, caused by Yersinia pestis. Rodents are the natural hosts with fleas as the vehicle of disease transmission. Domestic and wild dogs and cats have also been identified as possible disease hosts. In Zambia, plague outbreaks have been reported in the Southern and Eastern regions in the last 20 years. Based on these observations, Y. pestis could possibly be endemically present in the area.

Methods

To substantiate such possibility, sera samples were collected from rodents, shrews, dogs and cats for detection of antibodies against Fraction 1 gene (Fra1) of Y. pestis while organs from rodents and shrews, and fleas from both dogs and rodents were collected to investigate plasminogen activator gene (pla gene) of Y. pestis using ELISA and PCR respectively.

Results

A total of 369 blood samples were collected from domestic carnivores, shrews and domestic and peri-domestic rodents while 199 organs were collected from the rodents and shrews. Blood samples were tested for antibodies against Fra1 antigen using ELISA and 3% (5/165) (95% CI 0.99–6.93%) dogs were positive while all cats were negative. Of 199 sera from rodents and shrews, 12.6% (95% CI 8.30–17.98%) were positive for antibodies against Fra1 using anti-rat IgG secondary antibody while using anti-mouse IgG secondary antibody, 17.6% (95% CI 12.57–23.60%) were positive. PCR was run on the organs and 2.5% (95% CI 0.82–5.77%) were positive for plasminogen activator gene of Y. pestis and the amplicons were sequenced and showed 99% identity with Y. pestis reference sequences. All 82 fleas collected from animals subjected to PCR, were negative for pla gene. The specific rat-flea and dog-flea indices were 0.19 and 0.27 respectively, which were lower than the level required to enhance chances of the disease outbreak.

Conclusions

We concluded that plague was still endemic in the area and the disease may infect human beings if contact is enhanced between reservoir hosts and flea vectors. The lower specific rodent-flea Indices and absence of Y. pestis in the potential vectors were considered to be partly responsible for the current absence of plague outbreaks despite its presence in the sylvatic cycle.

Isolation of Bacillus anthracis from soil in selected high-risk areas of Zimbabwe

AIMS

To isolate Bacillus anthracis from cattle carcass burial sites from high-risk districts in Zimbabwe.

METHODS AND RESULTS

Soil samples were collected from carcass burial sites from seven areas, including two national game parks. Samples were collected from top 5-10 cm, and for spore extraction, 25 g of soil was suspended in sterile distilled water overnight. Supernatants were filtered through 0.45-μm pore cellulose nitrate, deposits suspended in 5 ml phosphate-buffered saline, aliquoted and heated at temperature regimen of 65, 70, 75 and 80 °C for 15 min. Samples were plated onto PLET agar. B. anthracis isolates were identified using growth morphology and PCR detecting pXO1 and pXO2 virulence plasmids. From samples heated at 75 °C for 15 min, B. anthracis were isolated from 9 of 81 (11.1%) soil samples representing five of the seven sampled areas.

CONCLUSIONS

We isolated B. anthracis from soil collected from carcass burial sites. PCR targeting virulence plasmids provided a rapid confirmation of B. anthracis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The positive isolation indicated that some carcass burial sites may retain viable spores for at least 12 months after the previous outbreak, which suggests that they may be important sources of B. anthracis and new disease outbreaks.

Detection and characterization of Clostridium species in soil of Zambia

In the retrospective study of soil-borne diseases of cattle in Zambia, malignant edema and blackquarter were widespread. One hundred and sixty-five cases with malignant edema and 103 cases with blackquarter were reported between 1985 and 1997. It was found that specific soil-conditions associate the emergence of the soil-borne diseases. Soil samples from five areas in Zambia were examined for the presence of genus Clostridium. Direct immunofluorescent assay (IFA) examination showed that C. septicum, C. novyi and C. chauvoei were detected in the soil of specific areas in Zambia, respectively. Causal organisms such as C. perfringens were isolated from the soil samples. The information of area-specific distribution of Clositridium species may give an efficient program in protecting cattle and man.

Occurrence of Salmonella enteritidis in pooled table eggs and market-ready chicken carcasses in Zambia

The level of Salmonella enteritidis contamination in Zambian table eggs and ready market chicken carcasses was studied. Nine of the 240 (3.8%) pooled samples of table eggs and 18 of 382 (4.7%) chicken carcasses were contaminated with S. enteritidis. All the isolates from the table eggs belonged to the enteropathogenic invasive phage type 4, whereas seven isolates from the chicken carcasses belonged to phage type 4, three were phage type 7, and eight were untypable (rough type). All the isolates were sensitive to gentamycin, ampicillin, tetracycline, cotrimoxazole, amoxycillin, furazolidone, and chloramphenicol.