A. K. M. A. Rahman

Bayesian estimation of true prevalence, sensitivity and specificity of indirect ELISA, Rose Bengal Test and Slow Agglutination Test for the diagnosis of brucellosis in sheep and goats in Bangladesh

The true prevalence of brucellosis and diagnostic test characteristics of three conditionally dependent serological tests were estimated using the Bayesian approach in goats and sheep populations of Bangladesh. Serum samples from a random selection of 636 goats and 1044 sheep were tested in parallel by indirect ELISA (iELISA), Rose Bengal Test (RBT) and Slow Agglutination Test (SAT). The true prevalence of brucellosis in goats and sheep were estimated as 1% (95% credibility interval (CrI): 0.7-1.8) and 1.2% (95% CrI: 0.6-2.2) respectively. The sensitivity of iELISA was 92.9% in goats and 92.0% in sheep with corresponding specificities of 96.5% and 99.5% respectively. The sensitivity and specificity estimates of RBT were 80.2% and 99.6% in goats and 82.8% and 98.3% in sheep. The sensitivity and specificity of SAT were 57.1% and 99.3% in goats and 72.0% and 98.6% in sheep. In this study, three conditionally dependent serological tests for the diagnosis of small ruminant brucellosis in Bangladesh were validated. Considerable conditional dependence between IELISA and RBT and between RBT and SAT was observed among sheep. The influence of the priors on the model fit and estimated parameter values was checked using sensitivity analysis. In multiple test validation, conditional dependence should not be ignored when the tests are in fact conditionally dependent.

Seroprevalence and risk factors for brucellosis in a high-risk group of individuals in Bangladesh.

Brucellosis is an occupational hazard of livestock farmers, dairy workers, veterinarians, slaughterhouse workers, and laboratory personnel, all of whom are considered to belong to the high-risk occupational group (HROG). A study was undertaken to determine the seroprevalence of brucellosis, identify risk factors associated with brucellosis seropositivity, and detect Brucella at genus level using real-time polymerase chain reaction (PCR) among people in the HROG in the Dhaka division of Bangladesh. A sample of 500 individuals from the HROG was collected from three districts of Dhaka division of Bangladesh. A multiple random effects logistic regression model was used to identify potential risk factors. Two types of real-time PCR methods were applied to detect Brucella genus-specific DNA using serum from seropositive patients. The prevalence of brucellosis based on the three tests was observed to be 4.4% based on a parallel interpretation. The results of the multiple random effects logistic regression analysis with random intercept for district revealed that the odds of brucellosis seropositivity among individuals who had been in contact with livestock for more than 26 years was about 14 times higher as compared to those who had less than 5 years of contact with livestock. In addition, when the contact was with goats, the odds of brucellosis seropositivity were about 60 times higher as compared to when contact was with cattle only. Noticeable variation in brucellosis seropositivity among humans within the three districts was noted. All of the 13 individuals who tested positive for the serological tests were also positive in two types of real-time PCR using the same serum samples. Livestock farmers of brucellosis positive herds had a significantly higher probability to be seropositive for brucellosis. The study emphasized that contact with livestock, especially goats, is a significant risk factor for the transmission of brucellosis among individuals in the HROG.

Seroprevalence of brucellosis in patients with prolonged fever in Bangladesh

INTRODUCTION This study describes the seroprevalence of human brucellosis among pyretic patients and detection of Brucella abortus DNA from seropositive pyretic patients using real-time polymerase chain reaction (rtPCR) for the first time in Bangladesh. METHODOLOGY Blood samples were collected from 300 pyretic patients from October 2007 to May 2008 and subjected to three serological tests: Rose-Bengal plate test (RBT), standard tube agglutination test (STAT), and indirect enzyme-linked immunosorbent assay (iELISA). Risk factors were identified by multivariate Firths logistic regression analysis. Brucella genus (BCSP31) and species-specific (IS711) rtPCR were applied to six human sera samples. RESULTS The seroprevalence of brucellosis among pyretic patients was estimated to be 2.0% (95% confidence interval [CI]: 0.74-4.30). The odds of brucellosis seropositivity were 8.9 (95% CI: 1.26-63.0) times higher in pyretic patients who handled goats than those who handled only cattle, whereas the odds of brucellosis seropositivity were 9.7 (95% CI: 1.28-73.68) times higher in pyretic patients who had backache compared to those without backache. B. abortus DNA was amplified from all six human sera that tested positive by RBT, STAT, and iELISA. As the agreement between the tests was very strong, RBT is recommended as a screening test for the diagnosis of human brucellosis in Bangladesh because it is easier to use, cheaper, and faster. CONCLUSIONS Brucellosis among pyretic patients is common, and B. abortus is responsible for brucellosis in such patients. Pyretic patients who handle goats and those with backaches should be screened for brucellosis.

Serological and Molecular Evidence of Q Fever in Domestic Ruminants in Bangladesh

The objective of this study was to know the herd and animal level prevalence of Q fever in domestic ruminants in some selected districts in Bangladesh. Randomly collected 111 bulk milk and 94 sera samples of cattle, sheep, and goats were tested by indirect ELISA (iELISA). DNA extracted from 23 aborted fetal membranes was analyzed by real time (rt) PCR. The positive cut-off value of iELISA in bulk milk and individual animal sera was ≥30% and ≥40%, respectively. The overall herd level prevalence of Q fever in dairy cattle was 15.6%. The prevalence of Q fever in dairy cattle was significantly higher in Sirajganj in comparison to Satkhira District (P < 0.01). The overall seroprevalence of Q fever in domestic ruminants was 5.06%. Although statistically insignificant, the seroprevalence of Q fever was relatively higher in sheep (9.52%) in comparison to goats (3.33%) and cattle (3.57%). Out of 23 aborted fetal membranes, only one sheep placenta was positive in rt PCR. Q fever is present in all of the three important species of domestic ruminants in Bangladesh. It may have some role in sheep abortion as the seroprevalence is relatively higher and also one sheep placenta is rt PCR positive.

Fascioliasis risk factors and space-time clusters in domestic ruminants in Bangladesh

BackgroundA retrospective observational study was conducted to identify fascioliasis hotspots, clusters, potential risk factors and to map fascioliasis risk in domestic ruminants in Bangladesh. Cases of fascioliasis in cattle, buffalo, sheep and goats from all districts in Bangladesh between 2011 and 2013 were identified via secondary surveillance data from the Department of Livestock Services’ Epidemiology Unit. From each case report, date of report, species affected and district data were extracted. The total number of domestic ruminants in each district was used to calculate fascioliasis cases per ten thousand animals at risk per district, and this was used for cluster and hotspot analysis. Clustering was assessed with Moran’s spatial autocorrelation statistic, hotspots with the local indicator of spatial association (LISA) statistic and space-time clusters with the scan statistic (Poisson model). The association between district fascioliasis prevalence and climate (temperature, precipitation), elevation, land cover and water bodies was investigated using a spatial regression model.ResultsA total of 1,723,971 cases of fascioliasis were reported in the three-year study period in cattle (1,164,560), goats (424,314), buffalo (88,924) and sheep (46,173). A total of nine hotspots were identified; one of these persisted in each of the three years. Only two local clusters were found. Five space-time clusters located within 22 districts were also identified. Annual risk maps of fascioliasis cases correlated with the hotspots and clusters detected. Cultivated and managed (P < 0.001) and artificial surface (P = 0.04) land cover areas, and elevation (P = 0.003) were positively and negatively associated with fascioliasis in Bangladesh, respectively.ConclusionsResults indicate that due to land use characteristics some areas of Bangladesh are at greater risk of fascioliasis. The potential risk factors, hot spots and clusters identified in this study can be used to guide science-based treatment and control decisions for fascioliasis in Bangladesh and in other similar geo-climatic zones throughout the world.

The prevalence of Brucella abortus DNA in seropositive bovine sera in Bangladesh

Prevalence of brucellosis has been widely investigated on the basis of serological test in livestock but the information on the prevalence of Brucella species is scarce in Bangladesh. The objective of this work was to determine the prevalence of Brucella species in cattle and buffaloes in Bangladesh. For these purpose, a total of 799 serum samples of cattle and buffaloes were collected from different districts of Bangladesh. Out of 799 serum samples, 45 serum samples reacted positively to the Rose Bengal test (RBT); among the RBT positive serum, 14 sera were found to contain Brucella DNA by genus specific IS711 screening using quantitative real time PCR (qRT-PCR); and all the 14 qRT-PCR positive samples were found to contain specifically Brucella abortus DNA. This report confirms that B. abortus is endemic in cattle and buffaloes in Bangladesh. A combination of SAT-iLEISA and PCR could be effective for future eradication programmes. Key words: Brucellosis, cattle, buffalo, Bangladesh, serology, polymerase chain reaction (PCR).

Investigation of methicillin-resistant Staphylococcus aureus among clinical isolates from humans and animals by culture methods and multiplex PCR

BackgroundStaphylococcus aureus is responsible for large numbers of hospital-related and community-acquired infections. In this study, we investigated the presence of S. aureus and methicillin-resistant S. aureus (MRSA) in 100 samples from animals (55 cattle, 36 dogs, and 9 cats) and 150 samples from hospitalized human patients. The samples were collected from healthy and diseased animals and from diseased humans and included milk, wound swab, pus, exudates, nasal swab and diabetic ulcer. Initially, S. aureus was isolated and identified by colony morphology, Gram staining, and biochemical tests (catalase and coagulase tests). The S. aureus-positive samples were examined by polymerase chain reaction (PCR) to determine their MRSA status.ResultsOf the 100 animal samples, 29 were positive for S. aureus. Four samples (13.8%) from dogs were MRSA-positive, but samples from cattle and cats were MRSA-negative. Of the 150 human samples we collected, 64 were S. aureus-positive and, of these, 34 (53.1%) were MRSA-positive. Most (28%) of the MRSA samples were isolated from surgical wound swabs, followed by the pus from skin infections (11%), exudates from diabetic ulcers (6%), exudates from burns (4%), and aural swabs (3%). By contrast, a low MRSA detection rate (n = 4) was seen in the non-human isolates, where all MRSA bacteria were isolated from nasal swabs from dogs. The antimicrobials susceptibility testing results showed that S. aureus isolates with mecA genes showed resistance to penicillin (100%), oxacillin (100%), erythromycin (73.5%), ciprofloxacin (70.6%), and gentamicin (67.7%). The lowest resistance was found against ceftazidime, and no vancomycin-resistant isolates were obtained.ConclusionsWe detected S. aureus and MRSA in both human and canine specimens. Isolates were found to be resistant to some of the antimicrobials available locally. MRSA carriage in humans and animals appears to be a great threat to effective antimicrobials treatment. The prudent use of antimicrobials will reduce the antimicrobial resistance. Our findings will help to find the most appropriate treatment and to reduce antimicrobial resistance in the future by implementing prudent use of antimicrobials. Further studies are required to better understand the epidemiology of MRSA human–animal inter-species transmission in Bangladesh.

Brucella abortus is Prevalent in Both Humans and Animals in Bangladesh.

To determine the role of different Brucella (B.) spp. in Bangladesh, 62 animal samples and 500 human sera were tested. Animal samples from cattle, goats and sheep (including milk, bull semen, vaginal swabs and placentas) were cultured for Brucella spp. Three test‐positive human sera and all animal samples were screened by Brucella genus‐specific real‐time PCR (RT‐PCR), and positive samples were then tested by IS711 RT‐PCR to detect B. abortus and B. melitensis DNA. Only B. abortus DNA was amplified from 13 human and six animal samples. This is the first report describing B. abortus as the aetiological agent of brucellosis in occupationally exposed humans in Bangladesh. Of note is failure to detect B. melitensis DNA, the species most often associated with human brucellosis worldwide. Further studies are required to explore the occurrence of Brucella melitensis in Bangladesh.

Bovine fascioliasis risk factors and space-time clusters in Mymensingh, Bangladesh

A hospital-based case-control study was undertaken to identify risk factors for - and space-time clusters of - bovine fascioliasis in Mymensingh, Bangladesh. Fascioliasis cases diagnosed using fecal sample test between January 2006 and December 2015 (n=593) at the Bangladesh Agricultural University Veterinary Teaching Hospital (BAUVTH) and three controls per case (n=1563) were selected. Data on date of report, location, age, breed, sex and body weight were extracted from the hospital records. A mixed multivariable logistic regression model with location as a random effect was built to identify risk factors for fascioliasis. The scan statistic (Bernoulli model) was used to identify space-time clusters. Compared to cattle ≤1year of age, the odds of fascioliasis were 5.2- (95% confidence interval [CI]: 3.6-7.4), 6.1- (95% CI: 4.2-8.7) and 10.7-times (95% CI: 6.9-16.6) greater in cattle aged >1-3, >3-8 and >8years, respectively. The odds of fascioliasis were 1.4- (95% CI: 1.03-1.99) and 1.5-times (95% CI: 1.13-2.11) greater in post-monsoon and monsoon seasons, respectively, compared to winter. Five significant (P<0.05) clusters (7-13 locations each) were identified, lasting from six months to 5years. Six locations - Bhangnamari, Deuhakhola, Gauripur, Ishwarganj, Nandail and Rasulpur - appeared to be at more risk for fascioliasis: these locations were part of at least 3 significant clusters. Anthelmintic treatment should focus on high risk age groups (>1year, especially those >8years). Importantly, we have demonstrated high-risk periods (monsoon and post-monsoon) and disease hotspots of bovine fascioliasis. Focusing disease control efforts in time and space offers an opportunity to more effectively control bovine fascioliasis in Bangladesh and in other similar geo-climatic zones throughout the world.