Exposure to bovine livestock and latent tuberculosis infection in children: investigating the zoonotic tuberculosis potential in a large urban and peri-urban area of Cameroon

Abstract

AbstractBackgroundBovine tuberculosis (bTB), a neglected zoonotic disease, is endemic in cattle in many Sub-saharan African countries, yet its contribution to tuberculosis (TB) burden is understudied. Rapid urbanisation and increase in demand for animal proteins, including dairy products, increases the risk of spill over. This study compared the latent tuberculosis infection (LTBI) risk in children, a proxy-measure for recent TB infection, in children living in high cattle density areas to children from the general population in Cameroon.MethodCross-sectional study in the Centre Region of Cameroon in 2021, recruiting 160 children aged 2-15 years, stratified by exposure to livestock, people treated for pulmonary TB (PTB) and the general community. Veinous blood was tested for LTBI using QuantiFERON–TB Gold-Plus. Prevalences were calculated and the association to exposure and other risk factors investigated using logistic regression models.ResultsThe crude LTBI prevalence were 8.2% in the general population, 7.3% in those exposed to cattle and 61% in pulmonary TB household contacts. After adjusting for confounding and sampling design, exposure to cattle and exposure to pulmonary TB were associated with higher risk of LTBI than the general population (respectively odds ratio (OR): 3.56, 95%CI: 0.34 to 37.03; and OR: 10.36, 95%CI: 3.13 to 34.21). Children frequently consuming cow milk had higher risk of LTBI (OR: 3.35; 95%CI 0.18 to 60.94).ConclusionDespite limited statistical power, this study suggests that children exposed to cattle in a setting endemic for bTB had higher risk of LTBI, providing indirect evidence thatMycobacterium bovismay contribute to TB burden.Author SummaryTuberculosis (TB) is the top infectious disease killer worldwide.Mycobacterium bovis(M. bovis) is the most common zoonotic and second most common cause of TB in humans. The pathogen is naturally resistant to pyrazinamide, a key component of standard anti-tuberculosis treatment, thus can hamper TB control and elimination efforts.M. bovisis endemic in cattle in this setting, but there is limited information on its contribution to TB burden. We used a specific test, the Interferon Gamma Released Assay, to compare latent TB infection (LTBI) rates in a random sample of children with high exposure to cattle, to that of children from the general community and from households with known pulmonary TB patient in and around a major urban centre in Cameroon; LTBI in children provide insight on recent infection, thus transmission. After adjusting for background differences, we found that exposure to cattle was associated with over three times higher risk of LTBI compared to the general population (and household exposure associated with over 10 times higher risk of infection). Our results suggest that exposure to cattle (thereforeM. bovis) contributes significantly to TB burden, and should be investigated thoroughly to support control efforts.