Seroprevalence and risk factors for human brucellosis in agro-pastoral areas in Tanzania

Background: Brucellosis is an endemic zoonosis in Tanzania. This study was conducted to investigate the seroprevalence of human brucellosis and its risk factors in agro-pastoral areas in Morogoro Region, Tanzania. Methods: Questionnaire survey and blood sampling were conducted from January to February 2018 at four villages. Anyone living in the villages and wished to participate were involved. Competitive ELISA was used for diagnosis. Risk factor analysis for sero-positivity in human and analysis for the association of sero-positivity between cattle and human within each farm were conducted, using the data of farm-level bovine brucellosis status from our bovine brucellosis research performed in 2016. Results: The seroprevalence was 33.3% (44/132). In univariable analysis, the Maasai were significantly more sero-positive (56.5%) than other tribes (28.4%) (OR = 3.23, 95% CI: 1.28–8.41). Drinking raw milk was a risk factor in both univariable and multivariable analyses (OR = 3.97, 95% CI: 1.61–10.20). A negative association between sero-positivity in cattle and human within each farm was found (p<0.01). The Maasai performed more risk-taking behaviours for human infection than other tribes: drinking raw milk (p<0.01) or blood (p<0.01) and helping delivery of cattle with bare hands (p=0.03). Conclusions: The Maasai were at high risk of human brucellosis. More detailed survey and educational interventions are urgently needed

Prevalence of the Staphylococcal Enterotoxins Genes in Raw and Milk Products along the Value Chain in Mbeya and Mbozi Districts, Tanzania

The study determined the prevalence of genes coding for Staphylococcal enterotoxins (SEs) from Staphylococcus aureus isolates in milk produced and sold in Mbeya and Mbozi districts in Tanzania. Samples of raw milk (n=300), boiled hot (ready-to-consume) milk (n=72) and sour milk (n=72) were randomly collected from smallholder dairy farmers, milk collection points (MCP) and milk shops. Laboratory analysis showed that 59.7% of the milk samples contained Staphylococcus species. Biochemical tests showed that 12.4% of the isolates were positive for S. aureus, of which 5.6, 2.5 and 4.3% were from samples collected from farmer’s herd milk, MCP and milk shops, respectively. Furthermore, multiplex Polymerase Chain Reaction (mPCR) results showed that 36.4% of the total S. aureus isolates (n=55) had SEs genes. Frequently observed gene was Sea (32.6%) while Sej was not detected in any of the isolates. The distribution of the SEs genes along the milk market channel showed 35, 15 and 50% of the genes came from isolates samples collected at farm level, MCP and milk shops, respectively. Moreover, no statistical difference were observed for SE coding gene between the districts and seasons, though higher (65%) prevalence of S. aureus isolates carrying SEs genes were observed in dry than wet season (35%). The prevalence of SE coding gene in raw, boiled hot and sour milk were 4.3, 5.6 and 4.2%, respectively. The results obtained show that milk produced and marketed in the two districts contained S. aureus isolates expressing gene for enterotoxins production which pose a potential public health risk. Hence, the results indicate the need to institute proper hygienic measures by all milk stakeholders in order to avoid contamination of milk with S. aureus. Further studies on the diversity and distribution of enterotoxins producing S. aureus in the Southern highlands and other areas in the country are recommended. Keywords: Boiled hot milk, sour milk, enterotoxins, Staphylococcus aureus, Multiplex PC

Quantitative evaluation of the infection dynamics of bovine brucellosis in Tanzania

Brucellosis is endemic in Tanzania. A cross-sectional study was conducted at 17 cattle farms in agro-pastoral areas in Tanzania to identify risk factors associated with the within-farm prevalence of bovine brucellosis and to quantitatively assess the infection dynamics through disease modelling. Cattle blood sampling and interviews with farmers using a structured questionnaire were conducted. A total of 673 serum samples were screened using the Rose-Bengal plate test (RBPT), and sero-positivity of RBPT-positive samples was confirmed using a competitive enzyme-linked immunosorbent assay. Zero-inflated binomial regression was performed for univariable and multivariable risk factor analyses of within-farm prevalence. Several susceptible-infectious (SI) models were compared based on deviance information criteria, and age-dependent force of infection (FOI) was measured using age-specific prevalence data for the 10 infection-positive farms. Using the diagnoses of cows on the 17 farms, the basic reproduction number, R0, was also calculated. The farm-level prevalence and animal-level adjusted prevalence were 58.8 % (10/17, 95 % confidence interval: 33.5–80.6 %) and 7.0 % (28/673, 95 % credible interval: 5.7–8.4 %), respectively. The risk factor for high within-farm prevalence was introduction of cattle from other herds. A mathematical model with constant FOI showed the annual probability of infection as 1.4 % (95 % credible interval: 1.0 %–2.0 %). The R0 was 1.07. The constant FOI could have been due to the predominant mode of infection being transmission of Brucella from contaminated aborted materials during grazing. Direct purchase of infected cattle could facilitate efficient transmission between susceptible animals through abortion

Quantitative evaluation of the infection dynamics of bovine brucellosis in Tanzania

International audienceBrucellosis is endemic in Tanzania. A cross-sectional study was conducted at 17 cattle farms in agro-pastoral areas in Tanzania to identify risk factors associated with the within-farm prevalence of bovine brucellosis and to quantitatively assess the infection dynamics through disease modelling. Cattle blood sampling and interviews with farmers using a structured questionnaire were conducted. A total of 673 serum samples were screened using the Rose-Bengal plate test (RBPT), and sero-positivity of RBPT-positive samples was confirmed using a competitive enzyme-linked immunosorbent assay. Zero-inflated binomial regression was performed for univariable and multivariable risk factor analyses of within-farm prevalence. Several susceptible-infectious (SI) models were compared based on deviance information criteria, and age-dependent force of infection (FOI) was measured using age-specific prevalence data for the 10 infection-positive farms. Using the diagnoses of cows on the 17 farms, the basic reproduction number, R0, was also calculated. The farm-level prevalence and animal-level adjusted prevalence were 58.8 % (10/17, 95 % confidence interval: 33.5–80.6 %) and 7.0 % (28/673, 95 % credible interval: 5.7–8.4 %), respectively. The risk factor for high within-farm prevalence was introduction of cattle from other herds. A mathematical model with constant FOI showed the annual probability of infection as 1.4 % (95 % credible interval: 1.0 %–2.0 %). The R0 was 1.07. The constant FOI could have been due to the predominant mode of infection being transmission of Brucella from contaminated aborted materials during grazing. Direct purchase of infected cattle could facilitate efficient transmission between susceptible animals through abortion

Toxigenic Vibrio cholerae O1 in vegetables and fish raised in wastewater irrigated fields and stabilization ponds during a non-cholera outbreak period in Morogoro, Tanzania:an environmental health study

BACKGROUND: Cholera, one of the world’s deadliest infectious diseases, remains rampant and frequent in Tanzania and thus hinders existing control measures. The present study was undertaken to evaluate the occurrence of toxigenic Vibrio cholerae O1 in wastewater, fish and vegetables during a non-outbreak period in Morogoro, Tanzania. METHODS: From October 2014 to February 2015, 60 wastewater samples, 60 fish samples from sewage stabilization ponds and 60 wastewater irrigated vegetable samples were collected. Samples were cultured for identification of V. cholerae using conventional bacteriological methods. Isolates were confirmed as V. cholerae by detection of the outer membrane protein gene (ompW) using polymerase chain reaction (PCR). Isolates were further tested for antibiotic susceptibility and presence of virulence genes including, cholera enterotoxin gene (ctx), the toxin co-regulated pilus gene (tcpA) and the haemolysin gene (hlyA). RESULTS: The prevalence of V. cholerae in wastewater, vegetables and fish was 36.7, 21.7 and 23.3 %, respectively. Two isolates from fish gills were V. cholerae O1 and tested positive for ctx and tcpA. One of these contained in addition the hlyA gene while five isolates from fish intestines tested positive for tcpA. All V. cholerae isolates were resistant to ampicillin, amoxicillin and some to tetracycline, but sensitive to gentamicin, chloramphenicol, and ciprofloxacin. CONCLUSIONS: Our results show that toxigenic and drug-resistant V. cholerae O1 species are present and persist in aquatic environments during a non-cholera outbreak period. This is of public health importance and shows that such environments may be important as reservoirs and in the transmission of V. cholerae O1