Wainaina, M. | bioRxiv Science

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↗

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↗