Biology subjects

Bett, B.

Publications and source records attributed to Bett, B..

5 recordsLinked to original sources

bioRxiv2022

Mapping the risk of Rift Valley fever in Uganda using national seroprevalence data from cattle, sheep and goats

Uganda has had repeated outbreaks of Rift Valley fever (RVF) since March 2016 when human and livestock cases were reported in Kabale after a long interval. The disease has a complex and poorly described transmission patterns which involves several mosquito vectors and mammalian hosts (including humans). We conducted a national serosurvey in livestock to determine RVF virus (RVFV) seroprevalence, risk factors, and to develop a risk map that could be used to guide risk-based surveillance and control measures. A total of 3,281 animals from 189 herds were sampled. Serum samples collected were screened at the National Animal Disease Diagnostics and Epidemiology Unit (NADDEC) using a competition multispecies anti-RVF IgG ELISA kit. Data obtained were analyzed using a Bayesian model that utilizes integrated nested Laplace approximation (INLA) and stochastic partial differential equation (SPDE) approaches to estimate posterior distributions of model parameters, and account for spatial autocorrelation that was detected in the data based on Morans I test. Variables considered included animal level factors (age, sex, species) and multiple environmental data including meteorological factors, soil types, and altitude. A risk map was produced by projecting fitted (mean) values, from a final model that had environmental factors onto a spatial grid that covered the entire domain. The overall RVFV seroprevalence was 11.39% (95% confidence interval: 10.35 - 12.51%). Higher RVFV seroprevalences were observed in older animals compared to the young, and cattle compared to sheep and goats. RVFV seroprevalence was also higher in areas that had (i) lower precipitation seasonality, (ii) haplic planosols, and (iii) lower cattle density. The risk map generated demonstrated that RVF virus was endemic in several regions including those that have not reported clinical outbreaks in the northeastern part of the country. This work has improved our understanding on spatial distribution of RVFV risk in the country as well as RVF burden in livestock. Author summaryOutbreaks of Rift Valley fever occur periodically in Uganda in livestock and humans. An Initial outbreak was reported in Kabale in March 2016 after a long quiescent period. Factors that trigger these outbreaks have not been fully described, but above-normal precipitation and flooding are known to be important causes. This paper presents a study that was conducted in the country to analyse RVF virus seroprevalence and risk factors for exposure in livestock. The study also mapped spatial distribution of RVFV seroprevalence. Data used in the study were generated from a national cross-sectional serosurvey that involved cattle, sheep and goats. Results obtained showed that the national RVFV seroprevalence was 11.39%, with 95% confidence interval of 10.35 - 12.51%. Cattle had higher RVFV seroprevalence compared to sheep and goats. Environmental factors that were associated with increased seroprevalence were low precipitation seasonality, haplic planosols, and low cattle density. Prevalence maps generated showed that the southwestern, central and parts of the northeastern regions had higher seroprevalence compared to other regions of the country. These can be used to guide the surveillance of the disease in the country.

microbiology↗

bioRxiv2020

Leptospira spp. seroprevalence in humans involved in a cross-sectional study in Garissa and Tana River Counties, Kenya

IntroductionLeptospirosis is a neglected bacterial zoonotic infection caused by spirochetes of Leptospira genus. Humans get infected through direct or indirect contact with urine of infected animals or environment. It accounts for more than 300,000 severe cases annually worldwide with case fatality rates of over 30%. Costs of diagnosis and treatment for human and animals, disruption of international trade of animals and products, reduced productivity and reproductivity in animals constitute economic importance. In Kenya, leptospirosis burden is significant but under-diagnosis and under-reporting affects the awareness of the disease. This study aimed to determine and compare the sero-prevalence and factors associated with Leptospira spp. in the two counties. MethodsWe conducted a cross-sectional study that involved apparently healthy people of at least 5 years of age in randomly selected households in Garissa and Tana River Counties. Blood samples were collected and tested for Leptospira spp antibodies using IgM ELISA. Standardized structured questionnaires were administered to collect socio-demographic and exposure information. We calculated frequencies and proportions for categorical variables and odds ratios (OR) and 95% confidence interval (CI) to evaluate association between sero-positivity and exposure factors. We used Wilcoxon test to evaluate statistical difference in sero-positivity for continuous variables and calculated test statistic (H) and p-value. ResultsA total of 952 subjects were recruited into the study - these included 482 persons from Garissa and 470 from Tana River. The overall sero-prevalence was 26% [(244/952); (CI: 23% to 29%)]. Garissa County had significantly higher Leptospira spp. seroprevalence (31%, n = 147; CI: 27% to 35%) compared to Tana River County (21 %, n = 97; CI: 17% to 25%). Being a female (OR=1.6, CI: 1.2-2.2) and engaging in pastoralism (OR=2.7, CI: 1.8-3.9) were significantly associated with higher odds of Leptospira spp. seropositivity compared to being a male or working in irrigated areas. The mean altitude of residence of sero-positive patients was 73m {+/-} 21 SD (standard deviation) above sea level and that for sero-negative was 80m {+/-} 22 SD (H=35, p-value = 0.00). ConclusionThis study determined the seroprevalence and risk factors for Leptospira spp. exposure in Garissa and Tana River Counties, Kenya. Females in pastoral communities experience high burden of the disease. Enhanced surveillance in humans and animals and further research is required to understand the complex and multifactorial drivers of leptospirosis transmission in the two Counties.

microbiology↗

bioRxiv2020

Incidence of Brucella spp. in various livestock species raised under the pastoral production system in Isiolo County, Kenya.

BackgroundBrucellosis is an important zoonosis with a worldwide distribution. The disease is caused by multiple species of Brucella that can infect a wide range of mammalian hosts. In the sub-Saharan Africa, many studies have been implemented to determine the prevalence of the disease in livestock, but not much is known about its incidence. We implemented a longitudinal study to determine the incidence of Brucella spp. infection in cattle, camels, sheep and goats that were being raised in a pastoral area in Isiolo County, northern Kenya. MethodsAn initial cross-sectional survey was implemented to identify unexposed animals for follow up; that survey used 141 camels, 216 cattle, 208 sheep and 161 goats. A subsequent longitudinal study recruited 31 cattle, 22 sheep, 32 goats and 30 camels for follow up. All the samples collected were screened for Brucella spp. using the Rose Bengal Plate test (RBPT), a modified RBPT, and an indirect multispecies Enzyme Linked Immunosorbent Assay (iELISA) kit. Samples that tested positive by any of these serological tests were further tested using real-time PCR-based assays to detect genus Brucella DNA and identify Brucella species. These analyses targeted the alkB and BMEI1162 genes for B. abortus, and B. melitensis, respectively. The longitudinal study took 12 months and data were analysed using Cox proportional hazards model that accounted for clustering of observations within herds. Changes in anti-Brucella IgG optical values between successive sampling periods were determined to confirm primary exposures. ResultsThe mean incidence rate of Brucella spp. was 0.024 (95% confidence interval [CI]: 0.014 - 0.037) cases per animal-months at risk. Brucella spp. incidence in camels, cattle, goats and sheep were 0.053 (0.022 - 0.104), 0.028 (0.010 - 0.061), 0.013 (0.003 - 0.036) and 0.006 (0.0002 - 0.034) cases per animal-month at risk, respectively. A higher incidence rate of Brucella spp. was found among females (0.020, 0.009 - 0.036) than males (0.016, 0.004 - 0.091), while young animals (0.026, 95% CI; 0.003 - 0.097) had a slightly higher incidence rate compared to adults (0.019, 95% CI; 0.009 - 0.034). RT PCR analyses showed that B. abortus was more prevalent than B. melitensis in the area. The results of multivariable Cox regression analysis identified species (camels and cattle) as an important predictor of Brucella spp. exposure in animals. On the diagnostic tests, modified RBPT provided similar findings as the iELISA test. ConclusionsOur findings indicated that camels and cattle have a higher incidence of Brucella spp. exposure than the other livestock species. This could be due to the higher prevalence of B. abortus, which readily infects these species, than B. melitensis. More studies are underway to identify ecological factors that influence the persistence of the key Brucella species in the area. The study further concluded that modified RBPT test can give reliable results as those of a formal iELISA test, and it can therefore be used for routine surveillance in the region. Author summaryBrucellosis is a neglected disease that is endemic in many pastoral areas. This study describes the incidence patterns of Brucella spp. in various livestock species (cattle, camels, sheep and goats) in Kinna in Isiolo County, northern Kenya. We also evaluated the diagnostic sensitivity of three serological tests; RBPT, a modified RBPT and an iELISA test in the diagnosis of brucellosis in animals that were suspected to be naturally exposed. Results from this study showed that both cattle and camels had a significantly higher incidence of Brucella spp. compared to sheep and goats. The number of animals found to be seropositive for Brucella spp. by the modified RBPT and iELISA did not differ significantly. Both tests also detected a significantly higher number of seropositive animals than RBPT. This finding confirms that the modified RBPT provides comparable results as iELISA, which is known to have higher sensitivity and specificity, and therefore the former can be used for more surveillance activities in pastoral areas.

microbiology↗

bioRxiv2019

Positive association between Brucella spp seroprevalences in livestock and humans from a cross-sectional study in Garissa and Tana River Counties, Kenya

BackgroundBrucella spp. is a zoonotic bacterial agent of high public health and socio-economic importance. It infects many species of animals including wildlife, and people may get exposed through direct contact with an infected animal or consumption of raw or undercooked animal products. We implemented a linked livestock-human cross-sectional study to determine seroprevalences and risk factors of Brucella spp. in livestock and humans. We also estimated intra-cluster correlation coefficients (ICCs) for these observations at the household and village levels.\n\nMethodologyThe study was implemented in Garissa County (specifically Ijara and Sangailu areas) and Tana River (Bura and Hola) counties. A household was the unit of analysis and the sample size was derived using the standard procedures. Serum samples were obtained from selected livestock and people from randomly selected households. Humans were sampled in both counties while livestock could be sampled only in Tana River County. Samples obtained were screened for anti-Brucella IgG antibodies using ELISA kits. Data were analyzed using generalized linear mixed effects logistic regression models with the household (herd) and village being used as random effects.\n\nResultsThe overall seroprevalences were 3.47% (95% confidence interval [CI]: 2.72 - 4.36%) and 35.81% (95% CI: 32.87 - 38.84) in livestock and humans, respectively. In livestock, older animals and those sampled in Hola had significantly higher seroprevalences that younger ones or those sampled in Bura. Herd and village random effects were significant and ICC estimates associated with these variables were 0.40 (95% CI: 0.22 - 0.60) and 0.24 (95% CI: 0.08 - 0.52), respectively. For human data, older people, males, and people who lived in pastoral areas had significantly higher Brucella spp. seroprevalences than younger ones, females or those who lived in irrigated or riverine areas. People from households that had at least one seropositive animal were 3.35 (95% CI: 1.51 - 7.41) times more likely to be seropositive compared to those that did not. Human exposures significantly clustered at the household level; the ICC estimate obtained was 0.21 (95% CI: 0.06 - 0.52).\n\nConclusionThe presence of a seropositive animal in a household significantly increased the risk of exposure in people in that household. Brucella spp. exposures in both livestock and humans clustered significantly at the household level. This suggests that risk-based surveillance measures, guided by locations of primary cases reported, either in humans or livestock, can be used to detect Brucella spp. infections livestock or humans, respectively.\n\nAuthor summaryBrucellosis is an important zoonotic disease that primarily affects livestock and wildlife. In humans, the disease is characterized by prolonged fever, body aches, joint pains and weakness while in livestock, the disease causes abortions and infertility. We carried out a study in northeastern Kenya (Garissa and Tana River Counties) to identify factors that affect the distribution of the disease in people and livestock. Livestock and people from randomly selected households were recruited and serum samples obtained for screening using anti-Brucella IgG ELISA kits to determine their Brucella spp. exposure. Data obtained were analyzed using mixed effects logistic regression models. Results obtained show that human and animal Brucella spp. seroprevalences cluster at the household level. The odds of exposure in humans were at least three times higher in households that had at least one seropositive animal compared to those that did not. These results can be used to design risk-based surveillance systems where each Brucella infection identified in livestock or humans could signal potential locations of other secondary infections.

epidemiology↗

bioRxiv2019

Contribution of livestock marketing chains and role played by stakeholders knowledge, attitude and practice in spreading cystic hydatidosis to Busia Town, Kenya, 2018.

BackgroundCystic hydatidosis (CH), a neglected parasitic zoonosis, is endemic in many parts of Kenya and could be spread along livestock marketing chains. Poor knowledge, attitude and practices (KAP) enables this spread in remote areas with inadequate public health services. We estimated prevalence, identified possible origin of CH to Busia, Kenya and assessed KAP among cattle owners and abattoir workers.\n\nMethods and Principal FindingsWe conducted a cross-sectional study on slaughtered livestock and interviewed their owners and abattoir workers in Busia in May-June 2018. We used visual observation, palpation and incision to identify cysts. Polymerase chain reaction (PCR) was used for confirmatory diagnosis. Epi Info 7 was used to calculate descriptive and associative statistics. Of 302 carcasses inspected, cysts were visualized in nine (2.98%, 95% Confidence Interval (CI): 1.46-5.78). Fourteen samples were collected and 13 (92.86%) were positive on PCR (sensitivity=92%, specificity=95%). All carcasses with cysts were from West Pokot County, which borders Busia to the north. We interviewed 310 participants: 260 were males (83.87%, 95% CI: 79.19 - 87.69); median age was 41 years (range=21-69). Dogs were kept by 221 (71.99%, 95% CI: 66.55 - 76.87), of which 83 (37.56%, 95% CI: 28.33 - 48.52) improperly disposed of dog faeces. Home slaughtering was practiced by 196 (63.23%, 95% CI: 58.78-69.80), of which 115 (58.67%, 95% CI: 51.44-65.64) were not inspected and 85 (43.37%, 95% CI: 36.32-50.62) fed raw organs to dogs. Adequate knowledge was associated with butcher ownership (P-value = 0.002), age [≥]35 years (P-value = 0.002) and higher literacy level (P-value <0.001).\n\nConclusions and SignificanceThere is non-negligible risk of CH in Busia communities which might worsen with time given that the county is connected to endemic areas through livestock trade. Poor KAP by the people on the disease calls for need to implement information, education and communication campaigns to improve KAP on CH in the area.\n\nAuthor summaryCystic hydatidosis is a globally neglected parasitic zoonosis which is endemic in many parts of the world including Kenya. It is majorly a problem among pastoral communities where there is close contact between human, livestock and dogs. Busia County, in Western Kenya is part of a livestock marketing chain between Kenya and Uganda. Animals from high endemic regions in Uganda and Kenya can easily spread the parasite to Busia through improper disposal of their infested organs. Non-pastoral communities like Busia may not have much cumulative experience about the disease though their practices may contribute to the perpetuation of the parasite in their environment. The parasite is gradually spreading to new areas and it is very important to the public health players in Kenya to take action so as to prevent further spread of this disease. Findings from this study show that the disease is no longer limited to pastoral communities only. There is need for the implementation of information, education and communication campaigns to improve the knowledge, attitude and practices of Busia community and other non-endemic regions on the disease.

epidemiology↗