Cattle‐associated risk factors for human tuberculosis in rural livestock‐keeping communities, Uganda

Systematic review of knowledge, attitudes, and practices of dairy farmers and consumers towards bovine tuberculosis in low- and middle-income countries

Bovine Tuberculosis (bTB), caused by Mycobacterium bovis, is a neglected zoonotic disease primarily associated with cattle. The incidence of bTB is highest in low-income settings with high cattle density and unpasteurised dairy consumption. Smallholder dairy farming has steadily grown in low- and middle-income countries (LMICs) with limited professional support for adequate bTB surveillance and risk mitigation. Several studies have explored the knowledge, attitudes, and practices (KAP) of milk value chain stakeholders towards bTB in LMICs, but this evidence has not been collated and synthesised. We conducted a systematic review to determine what is known, believed, and done in relation to bTB among dairy producers and consumers in LMICs. We performed a systematic search of studies in OVID Medline, Scopus and CABI on 11 September 2023. KAP data were summarised using narrative synthesis and forest plots. We retrieved 2763 articles, retaining 51 for the review. Only studies from Africa (n = 38) and Asia (n = 13) met the eligibility criteria. Most populations reported awareness of human tuberculosis and knew it could be treated, but there was limited awareness of bTB and its zoonotic potential. Knowledge of bTB transmission routes and bTB mitigation varied across populations, and risky practices were also variable. Inconsistencies in study design and survey tools suggest some results may have a mid- to high-risk of bias. Awareness of bTB is surprisingly low among African and Asian populations with high bTB exposure risk, possibly due to the long-standing divide between animal and human health messages that has obscured the One Health implications of bTB. Addressing bTB in LMICs requires a structural One Health approach and standard KAP survey tools to adequately explore the socio-cultural, political, and economic processes and drivers favouring bTB spread and persistence.

Associations between livestock keeping, morbidity and nutritional status of children and women in low- and middle-income countries: a systematic review

Livestock keeping can positively influence the nutritional status of populations and households through increased consumption of animal-source foods (ASF) and other indirect pathways, but can also adversely affect health by increasing the risk of diseases. We conducted a systematic review synthesising the current state of knowledge on the associations among livestock keeping, infectious disease and the nutritional status of children under 5 years and women of reproductive age in low- and lower-middle-income countries (LMICs). A comprehensive search of 12 electronic databases and grey literature sources published from 1991 to the end of December 2020 was conducted. Investigations exploring relationships between livestock keeping and risk of infectious disease transmission and nutritional status were selected using pre-defined inclusion criteria. After screening and filtering of 34,402 unique references, 176 references were included in the final synthesis. Most (160/176, 90.1%) of the references included in the final synthesis were from sub-Saharan Africa (SSA) and Asia. About two out of every five (42%) studies reviewed showed that livestock production is associated with improved height-for-age Z scores (HAZ) and weight-for-length/height Z scores (WHZ), while close to a third (30.7%) with improved weight-for-age Z scores (WAZ). Similarly, livestock production showed a positive or neutral relationship with women's nutritional status in almost all the references that reported on the topic. Conversely, four-fifths (66/81, 79.5%) of the references reporting on infection and morbidity outcomes indicated that livestock keeping is linked to a wide range of infectious disease outcomes, which are spread primarily through water, food and insects. In conclusion, in many LMIC settings, livestock production is associated with better nutritional outcomes but also a higher risk of disease transmission or morbidity among women and children.This review was prospectively registered on PROSPERO 2020 [CRD42020193622].

Bovine ownership and reduced pulmonary tuberculosis risk in Nepal: A case-control study

This case-control study sought to confirm and investigate in more depth protective associations previously found of bovine (cattle and water buffalo) ownership with reduced risk of both pulmonary tuberculosis (PTB) and latent tuberculosis infection (LTBI) in humans. The study recruited male and female PTB cases from a diagnostic centre and a frequency-matched community-based control group in Kaski District, Nepal. Controls were tested for LTBI status and a separate nested case-control study was conducted based on LTBI status. Data were collected on participant household animal ownership. Using logistic regression, animal ownership was investigated for associations with both PTB and LTBI. Data were obtained from 570 PTB cases and 1,224 controls, the latter group providing 396 LTBI-positive and 692 LTBI-negative subjects. Results provided evidence of decreased odds of both PTB and LTBI positivity associated with owning bovines. The evidence was strongest for protection against infection, rather than activation of infection to PTB. Effects were strongest in women, who usually manage the animals in Nepal, and there were exposure-response relationships with numbers of bovines owned. Results suggest that exposure to bovines is protective against LTBI and PTB. A possible mechanism involves boosting the effect of BCG (Bacillus Calmette-Guerin) vaccination, particularly in protecting against tuberculous infection. Additional studies with more extensive data collection are needed to confirm the observed associations.

Risk factors of tuberculosis in human and its association with cattle TB in Nepal: A one health approach

Tuberculosis (TB) in humans is primarily caused by Mycobacterium tuberculosis (M. tuberculosis), with millions of infections and hundreds of thousands of deaths worldwide. It creates a substantial economic burden on the community. Unlike M. tuberculosis, Mycobacterium bovis infects cattle and causes bovine TB, also known as zoonotic TB. People can contract zoonotic TB after consumption of unpasteurized dairy products, handling the sick animals, and via occupational exposures. The association between the zoonotic TB in humans and cattle is not well known in Nepal. The study examined the associated risk factors, including exposure to infected cattle, that contribute to TB's development in human beings in Nepal.

The study consists of human and animal subjects. Firstly, a retrospective matched case-control study was conducted at the National Tuberculosis Center (NTC), Bhaktapur, Nepal. A total of 290 people (equal numbers of TB cases and control subjects) were interviewed to obtain information on socio-demographic, behavioral, and occupational risks, including the history of cattle related exposures. Secondly, a cross-sectional study was performed among the cattle owned by the TB-confirmed patients. Comparative tuberculin skin test, rapid antibody test, and ELISA were used in parallel to detect M. bovis infection in cattle.

The risk factors for the development of TB in humans were smokers (OR = 4.6, 95% CI: 2.1–10.0, p < 0.001), previous history of TB (OR = 7.9, 95% CI: 3.0–20.6, p < 0.001) and history of cattle exposures (OR = 3.9, 95% CI: 2.1–7.4, p = 0.001). Out of 123 cattle sampled, 12 cattle (9.76%, 95% CI: 5.37–16.76, p < 0.0001) were positive by the tuberculin test, 46 (37.4%, 95% CI: 28.97–46.62, p = 0.007) were tested positive by the rapid test, and 7 (5.7%, 95% CI: 2.52–11.80, p < 0.0001) by ELISA test. The inter-test agreement between the tuberculin and ELISA was very strong (κ = 0.72, 95% CI: 0.48–0.95, p < 0.01).

This study indicates that exposure to infected cattle and socio-demographic risk factors can contribute to the development of TB in human beings.