Brucella abortus is Prevalent in Both Humans and Animals in Bangladesh

Prevalence and occupational exposure to zoonotic diseases in high-risk populations in the Free State Province, South Africa

Introduction

Zoonotic diseases are responsible for 2.5 billion human cases globally and approximately 2.7 million deaths annually. Surveillance of animal handlers and livestock for zoonotic pathogens contributes to understanding the true disease burden and risk factors within a community. This study investigated the prevalence of selected zoonoses in cattle, farm workers and occupational exposure to endemic zoonotic diseases and their associated risk factors.

Methods

Sputum samples from farmworkers were screened for Mycobacterium bovis. Blood specimens from farmworkers and archived sera were tested for serological evidence of Brucella sp., hantaviruses, and Leptospira sp. Communal and commercial cattle herds were tested for bovine tuberculosis and brucellosis.

Results

Mycobacterium bovis was not isolated from human samples. A total of 327 human sera were screened, and 35/327 (10.7%) were Brucella sp. IgG positive, 17/327 (5.2%) Leptospira sp. IgM positive, and 38/327 (11.6%) hantavirus IgG positive (95% CI). A higher proportion of Brucella sp. IgG-positive samples were detected among veterinarians (value of p = 0.0006). Additionally, two cattle from a commercial dairy farm were bovine tuberculosis (bTB) positive using the bTB skin test and confirmatory interferon-gamma assay. A higher percentage of confirmed brucellosis-positive animals were from communal herds (8.7%) compared to commercial herds (1.1%).

Discussion

These findings highlight the brucellosis and M. bovis prevalence in commercial and communal herds, the zoonotic disease risk in commercial and subsistence farming in developing countries, and the occupational and rural exposure risk to zoonotic pathogens.

Seroprevalence and risk factors for bovine brucellosis in the Chittagong Metropolitan Area of Bangladesh

Brucellosis is a neglected endemic zoonosis in Bangladesh and has a significant impact on public health and animal welfare of dairy farming as well as dairy farm economics. A cross‐sectional study was conducted to evaluate the seroprevalence of and risk factors for brucellosis in dairy cattle in the Chittagong metropolitan area (CMA) of Chittagong, Bangladesh. We collected serum samples (n = 158) from six randomly selected dairy farms in the CMA between February and November, 2015. The Rose Bengal Plate Test (RBPT) and a competitive ELISA (cELISA) were used as the screening and confirmatory tests respectively. Farm level and animal level demographic and risk factor data were collected using a questionnaire. The risk factors were analysed using a multivariable logistic regression with random effects. The overall seroprevalences of antibodies against brucellosis in cattle were 21.5% (34/158) and 7.6% (12/158) based on parallel and serial interpretation of the two tests respectively. Our results revealed that 20.3% (32/158) samples were positive using the RBPT and 8.9% (14/158) were positive using the cELISA. The within‐herd seroprevalence ranged from 10% to 26.3% and 5 to 20.7% using the RBPT and cELISA tests respectively. The odds of seropositivity were significantly higher in lactating cows (OR: 2.59; 95% CI: 1.02–6.55), cows producing less than 2 litres of milk (OR: 29.6; 95% CI: 4.3–353.8), cow producing 2–12 litres of milk (OR: 4.8; 95% CI: 1.1–33.4) and cows with reproductive disorders (OR: 3.2; 95% CI: 1.2–10.1). About 7.6% (12/158) and 1.3% (2/158) of cattle were found to be infected with acute and chronic brucellosis respectively. Based on these results, we suggest that cows that have reproductive disorders and are producing little milk should be prioritized for brucellosis screening in CMA. The screening tests should be used to control brucellosis in cattle in order to protect animal welfare, human health and to minimize the economic losses.

Bayesian evaluation of three serological tests for the diagnosis of bovine brucellosis in Bangladesh

We evaluated the performance of three serological tests – an immunoglobulin G indirect enzyme linked immunosorbent assay (iELISA), a Rose Bengal test and a slow agglutination test (SAT) – for the diagnosis of bovine brucellosis in Bangladesh. Cattle sera (n = 1360) sourced from Mymensingh district (MD) and a Government owned dairy farm (GF) were tested in parallel. We used a Bayesian latent class model that adjusted for the conditional dependence among the three tests and assumed constant diagnostic accuracy of the three tests in both populations. The sensitivity and specificity of the three tests varied from 84.6% to 93.7%, respectively. The true prevalences of bovine brucellosis in MD and the GF were 0.6% and 20.4%, respectively. Parallel interpretation of iELISA and SAT yielded the highest negative predictive values: 99.9% in MD and 99.6% in the GF; whereas serial interpretation of both iELISA and SAT produced the highest positive predictive value (PPV): 99.9% in the GF and also high PPV (98.9%) in MD. We recommend the use of both iELISA and SAT together and serial interpretation for culling and parallel interpretation for import decisions. Removal of brucellosis positive cattle will contribute to the control of brucellosis as a public health risk in Bangladesh.

Occupational history of exposure to zoonotic agents in people dedicated to livestock in San Pedro de los Milagros, Antioquia, Colombia

Introduction: According to the World Health Organization, livestock farming is one of the anthropic activities in which workers are exposed to various zoonotic agents.Objectives: To establish the frequency of seropositivity (IgG antibodies) against some zoonotic agents in people with occupational exposure to livestock in San Pedro de los Milagros (Antioquia), and to analyze associated factors.Materials and methods: Descriptive study carried out on a population of 328 cattle farmers. Demographic data were collected and the seropositivity frequency of IgG antibodies to Babesia bovis, Babesia bigemina, Anaplasma phagocytophilum, Ehrlichia chaffensis, Borrelia burgdorferi, Coxiella burnetii, Francisella tularensis, Brucella abortus, Brucella suis, Leptospira interrogans, and Toxoplasma gondii was determined. Overall and specific prevalence, prevalence ratios and binary logistic regressions were estimated.Results: The highest seropositivity frequencies were 47.6% for T. gondii, 33.5% for B. burgdorferi and 13% for E. chaffensis. The prevalence of T. gondii and B. burgdorferi had statistical association with sex [RP:1.3 (CI:1.0-1.8) and 2.0 (CI:1.1-3.9) respectively], and age group [(RP:1.5 (CI:1.2-1,9) and 2.5 (CI:1.4-6.4) respectively]. In workers with more than 10 years of related work experience, statistical association was 50% [RP:1.5 (CI:1.2-1.9) and 2.5 (CI:1.6-2.3), respectively]. There were no seropositive results for B. abortus, B. suis, B. bovis and B. bigemina.Conclusions: Exposure to some zoonotic agents was evidenced. This is determinant for the knowledge of tropical zoonotic diseases transmitted by vectors in livestock production systems.

First Genome Sequence of Brucella abortus Biovar 3 Strain BAU21/S4023, Isolated from a Dairy Cow in Bangladesh

We report the genome sequence of Brucella abortus biovar 3 strain BAU21/S4023, isolated from a dairy cow that suffered an abortion in Savar, Dhaka, Bangladesh. The genome sequence length is 3,244,234 bp with a 57.2% GC content, 3,147 coding DNA sequences (CDSs), 51 tRNAs, 1 transfer messenger RNA (tmRNA), and 3 rRNA genes.

We report the genome sequence of Brucella abortus biovar 3 strain BAU21/S4023, isolated from a dairy cow that suffered an abortion in Savar, Dhaka, Bangladesh. The genome sequence length is 3,244,234 bp with a 57.2% GC content, 3,147 coding DNA sequences (CDSs), 51 tRNAs, 1 transfer messenger RNA (tmRNA), and 3 rRNA genes.