Occupational Practices and Hazards of Rural Livestock Keepers in Uganda: A Cross-Sectional Study

Objective: In Uganda, 70% of rural poor rely on livestock for subsistence, to meet social obligations, and to insure against disaster. Livestock farming in Africa is in a state of transition from traditional management systems toward intensified modern systems, calling into question the future of traditional systems. To inform this debate, we conducted a survey in Moyo District, Uganda, to describe occupational practices and hazards of agropastoralist livestock keepers.   Methods: Household surveys were administered to heads of household (N=49) from July to September 2016. Cross-sectional data were used to generate descriptive statistics for livestock-associated practices and exposures. Logistic regression was used to estimate odds ratios and Wald-type 95% confidence intervals for risk factors for injury, defined as any animal-related injury in the household in the past year. Risk factors studied were total number of male animals; number of male cattle, sheep/goats, and pigs; proportion male by herd size; herd size; and castration practices.   Results: Adult men perform most livestock-associated tasks, while women, girls, and boys prepare meat, milk cattle, care for poultry, and dispose of waste. While 31 (63%) of households use professional veterinary services and most (n=28, 57.2%) are familiar with zoonoses, 25 (53.2%) do not believe sick animals may look healthy. Over 85.0% (n=41) of respondents routinely wash their hands, while only 31 (64.6%) use soap. Twenty-eight (57.0%) reported using personal protective equipment, while none used gloves or face protection. Most respondents had contact with animal waste “often”, and had contact with urine and blood “sometimes”. Six (12%) reported a needlestick injury while treating an animal, and 22 (45%) reported at least 1 injury from an animal. No significant association was found between the risk factors studied and animal injury, after adjustment for confounders.   Conclusions: Occupational risks for female and young agropastoralists are distinct from those of men. Contact with potentially infectious material is common and current practices – handwashing without soap and low glove use – do little to prevent zoonotic transmission. While agropastoralists are familiar with zoonoses, subclinical infections may be missed. While no significant risk factors were identified for animal injury, both animal and needlestick injuries are common. As livestock agriculture intensifies, these hazards will become more pronounced; drivers of risk behavior and animal injury must be identified to inform interventions to improve the occupational health of rural livestock keepers in Uganda

Optimizing HIV retesting during pregnancy and postpartum in four countries: a cost-effectiveness analysis.

INTRODUCTION: HIV retesting during late pregnancy and breastfeeding can help detect new maternal infections and prevent mother-to-child HIV transmission (MTCT), but the optimal timing and cost-effectiveness of maternal retesting remain uncertain. METHODS: We constructed deterministic models to assess the health and economic impact of maternal HIV retesting on a hypothetical population of pregnant women, following initial testing in pregnancy, on MTCT in four countries: South Africa and Kenya (high/intermediate HIV prevalence), and Colombia and Ukraine (low HIV prevalence). We evaluated six scenarios with varying retesting frequencies from late in antenatal care (ANC) through nine months postpartum. We compared strategies using incremental cost-effectiveness ratios (ICERs) over a 20-year time horizon using country-specific thresholds. RESULTS: We found maternal retesting once in late ANC with catch-up testing through six weeks postpartum was cost-effective in Kenya (ICER = $166 per DALY averted) and South Africa (ICER=$289 per DALY averted). This strategy prevented 19% (Kenya) and 12% (South Africa) of infant HIV infections. Adding one or two additional retests postpartum provided smaller benefits (1 to 2 percentage point increase in infections averted versus one retest). Adding three retests during the postpartum period averted additional infections (1 to 3 percentage point increase in infections averted versus one retest) but ICERs ($7639 and in Kenya and$11 985 in South Africa) greatly exceeded the cost-effectiveness thresholds. In Colombia and Ukraine, all retesting strategies exceeded the cost-effectiveness threshold and prevented few infant infections (up to 31 and 5 infections, respectively). CONCLUSIONS: In high HIV burden settings with MTCT rates similar to those seen in Kenya and South Africa, HIV retesting once in late ANC, with subsequent intervention, is the most cost-effective strategy for preventing infant HIV infections. In these settings, two HIV retests postpartum marginally reduced MTCT and were less costly than adding three retests. Retesting in low-burden settings with MTCT rates similar to Colombia and Ukraine was not cost-effective at any time point due to very low HIV prevalence and limited breastfeeding

Cost-effectiveness of dual maternal HIV and syphilis testing strategies in high and low HIV prevalence countries: a modelling study.

BACKGROUND: Dual HIV and syphilis testing might help to prevent mother-to-child transmission (MTCT) of HIV and syphilis through increased case detection and treatment. We aimed to model and assess the cost-effectiveness of dual testing during antenatal care in four countries with varying HIV and syphilis prevalence. METHODS: In this modelling study, we developed Markov models of HIV and syphilis in pregnant women to estimate costs and infant health outcomes of maternal testing at the first antenatal care visit with individual HIV and syphilis tests (base case) and at the first antenatal care visit with a dual rapid diagnostic test (scenario one). We additionally evaluated retesting during late antenatal care and at delivery with either individual tests (scenario two) or a dual rapid diagnosis test (scenario three). We modelled four countries: South Africa, Kenya, Colombia, and Ukraine. Strategies with an incremental cost-effectiveness ratio (ICER) less than the country-specific cost-effectiveness threshold (US$500 in Kenya,$750 in South Africa, $3000 in Colombia, and$1000 in Ukraine) per disability-adjusted life-year averted were considered cost-effective. FINDINGS: Routinely offering testing at the first antenatal care visit with a dual rapid diagnosis test was cost-saving compared with the base case in all four countries (ICER: -$26 in Kenya,-$559 in South Africa, -$844 in Colombia, and -$454 in Ukraine). Retesting during late antenatal care with a dual rapid diagnostic test (scenario three) was cost-effective compared with scenario one in all four countries (ICER: $270 in Kenya,$260 in South Africa, $2207 in Colombia, and$205 in Ukraine). INTERPRETATION: Incorporating dual rapid diagnostic tests in antenatal care can be cost-saving across countries with varying HIV prevalence. Countries should consider incorporating dual HIV and syphilis rapid diagnostic tests as the first test in antenatal care to support efforts to eliminate MTCT of HIV and syphilis. FUNDING: WHO, US Agency for International Development, and the Bill & Melinda Gates Foundation

Livestock and the epidemiology of sleeping sickness: mechanisms and implications

Thesis (Ph.D.)--University of Washington, 2021In recent decades, remarkable progress in the control of Human African trypanosomiasis (HAT)---a bloodborne protozoal parasite transmitted by the tsetse fly (Glossina species)---has led the WHO to set targets for elimination as public health problem (EPHP) by 2020, and elimination of transmission (EOT) by 2030. Global EPHP targets were met in 2018, however most endemic countries are not yet eligible for national EPHP validation, and there are significant challenges to achieving EOT goals. Two forms of HAT, which are geographically- and epidemiologically-distinct, exist: the chronic form, caused by Trypanosoma brucei gambiense (gHAT) and endemic in western and central Africa, and the acute form, caused by T. b. rhodesiense (rHAT) and endemic in eastern and southern Africa. Due to the known importance of animal reservoirs for rHAT EOT targets are set for gHAT alone, resulting in significantly lower investment in rHAT surveillance and control compared with gHAT. Combined with rHAT's acute progression this results in significant underreporting, raising concerns that rHAT will emerge as a major public health problem once gHAT EOT is achieved and donor attention moves away from HAT. With regards to gHAT, uncertainty surrounding animal reservoirs---in particular domestic pigs---as well as latent human reservoirs and undercoverage of high-risk groups by active surveillance activities threaten both the probability of EOT, and re-emergence following EOT. In this dissertation, we used data from the WHO Atlas of HAT, spatial epidemiologic methods, methods drawn from the potential outcomes framework of causal inference, and a stochastic compartmental model to estimate the effect of pig density on HAT risk, to evaluate the feasibility of rHAT EOT with control of domestic animal reservoirs alone, and to decompose the livestock density - HAT effect into three components: (1) the reservoir effect, whereby domestic cattle and pigs infected with trypanosomes serve as a source of human infection, (2) the zooprophylactic effect, whereby tsetse fly preference for livestock protects humans from bites---and therefore trypanosome infection---when livestock are nearby, and (3) the environmental change effect, whereby livestock keeping results in environmental changes that in turn modify tsetse distribution and HAT risk. We conducted this work in four high-burden countries which do not meet WHO criteria for EPHP validation: Uganda (gHAT and rHAT), South Sudan (gHAT), Malawi (rHAT), and Democratic Republic of Congo (DRC, gHAT). Our results suggest pigs may indeed be gHAT reservoirs and, if so, EOT will not be achieved without intervention---trypanocide or, preferably, insecticide treatment---on this reservoir. With regards to rHAT, we found control of the domestic cattle and pig reservoir is critical to control of the disease, in particular in Uganda, but does not lead to EOT. We found evidence of a zooprophlyactic effect in Malawi and South Sudan for both cattle and pigs and in gHAT foci in Uganda for cattle, however we did not detect compelling evidence of an environmental change effect. These results point to the utility of a One Health approach to HAT control, and represent an important contribution to the HAT literature and the efforts of National Sleeping Sickness Control Programs in the study countries. In conjunction with the high-resolution livestock density maps we have produced, our findings will support targeted delivery of expanded and/or enhanced HAT control efforts. Delivering these efforts in a One Health framework, whereby control of animal African trypanosomiasis is coordinated with that of HAT, will increase the likelihood and sustainability of gHAT elimination and ensure rHAT does not subsequently emerge as a major public health problem, reducing the burden of this highly-fatal and poverty-reinforcing disease

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

Thesis (Master's)--University of Washington, 2017-06Tuberculosis (TB) is a leading infectious cause of human death worldwide. TB can also infect cattle, resulting in productivity losses, trade barriers, and zoonotic transmission via milk, meat, or direct contact. While the majority of TB cases are non-zoonotic, an unknown proportion are acquired from cattle; in Africa, this proportion is estimated to be 0.4% to 10%. We conducted a cross-sectional study in rural communities in southeastern and northwestern Uganda between 2014 and 2016 to evaluate the association between tuberculosis skin test (TST) positivity in humans and cattle-associated risk factors. Human and cattle skin testing was performed in communities followed by a survey of household practices. TST data are available on 493 humans, 250 men and 243 women; 184 individuals in total—111 men and 73 women—tested positive. Separate log binomial models were fit to estimate relative risks (RR) for herd TST positivity stratified on gender and for raw milk consumption, using generalized estimating equations. Having at least one TST positive bovid in the household’s herd was significantly associated with decreased risk of TB among men (PR 0.61, 95% CI 0.47, 0.79) but was not significantly associated with TB among women (PR 1.26, 95% CI 0.80, 1.97). This was contrary our a priori hypothesis of higher effect of exposure among men—the primary caretakers of cattle—than women. This apparent protective effect may be the result of residual confounding by socioeconomic status: wealthier individuals may be less likely to be TB positive, but more likely to have TST positive herds by virtue of larger herd sizes, ability to purchase new and possibly infected stock, and propensity to keep more TB-susceptible European breeds. For raw milk consumption, effect estimates were close to one and not statistically significant; adjustment for confounders or pathways mediated by exposure to non-zoonotic TB did not change the size or magnitude of effect estimates. The importance of cattle-associated risk factors for human TB burden may be setting-specific, as suggested by the lack of consensus reached by prior research. In settings where bovine TB prevalence is low, such as Uganda, cattle-associated zoonotic transmission may be rare

The curse of dimensionality: Animal-related risk factors for pediatric diarrhea in western Kenya, and methods for dealing with a large number of predictors.

BackgroundPediatric diarrhea, a leading cause of under-five mortality, is predominantly infectious in etiology. As many putative causal agents are zoonotic, animal exposure is a likely risk factor. To evaluate the effect of animal-related factors on moderate to severe childhood diarrhea in rural Kenya, where animal contact is common, Conan et al. studied 73 matched case-control pairs from 2009-2011, collecting rich exposure data on many dimensions of animal contact. We review the challenges associated with analyzing moderately-sized datasets with a large number of predictors and present two alternative methodological approaches.Methodology/principal findingsWe conducted a simulation study to demonstrate that forward stepwise selection results in overfit models when data are high-dimensional, and that p values reported directly from the data used to train these models are misleading. We described how automated methods of variable selection, attractive when the number of predictors is large, can result in overadjustment bias. We proposed an alternative a priori regression approach not subject to this bias. Applied to Conan et al.'s data, this approach found a non-significant but positive trend for household's sharing of water sources with livestock or poultry, child's presence for poultry slaughter, and child's habit of playing where poultry sleep or defecate. For many predictors evaluated few pairs were discordant, suggesting matching compromised the power of this analysis. Finally, we proposed latent variable modeling as a complimentary approach and performed Item Response Theory modeling on Conan et al.'s data, with animal contact as the latent trait. We found a moderate but non-significant effect (OR 1.21, 95% CI 0.78, 1.87, unit = 1 standard deviation).Conclusions/significanceAutomated methods of model selection are appropriate for prediction models when fit and evaluated on separate samples. However when the goal is inference, these methods can produce misleading results. Furthermore, case-control matching should be done with caution

A mathematical model for evaluating the role of trypanocide treatment of cattle in the epidemiology and control of Trypanosoma brucei rhodesiense and T. b. gambiense sleeping sickness in Uganda

Background: Human and animal African trypanosomiases impose a large economic and health burden in their endemic regions. Large strides have been made in the control of human African trypanosomiasis (HAT), yet these efforts have largely focused on the non-zoonotic form of the disease. Using a mathematical model with a 10 year time horizon, we demonstrate the role of the cattle treatment with trypanocides in the epidemiology of zoonotic and non-zoonotic HAT in Uganda, and its potential implications on elimination and eradication of the disease. Methodology/principal findings: We created two compartmental, deterministic models, each comprised of three sub-models: humans, the tsetse fly vector (Glossina fuscipes fuscipes), and cattle. We applied these models to two HAT foci in Uganda: the gambiense (chronic, non-zoonotic) form in the Northern Region, and the rhodesiense (acute, zoonotic) form in the Eastern Region. Parameters were derived from prior literature or assumed. In both foci we assumed G. fuscipes fuscipes expresses zoophilic biting behavior.With trypanocide treatment of cattle administered every 3 months, treatment in stage I (representing engagement in active or passive surveillance) had a larger impact on HAT burden than cattle treatment coverage. However increasing cattle treatment coverage allowed for further reduction in prevalence in both foci. Using these model parameters, our estimated R0 suggests humans cannot alone sustain the HAT epidemic in Uganda. Conclusions/significance: Even in the absence of zoonotic transmission, loss of a preferred tsetse host species can affect HAT risk. Thus One Health strategies which integrate HAT and animal African trypanosomiasis control may improve the timeliness and sustainability of gHAT and rHAT elimination and eradication in Uganda. Furthermore, such strategies reduce the burden of a high-morbidity livestock disease of economic importance. Keywords: Human African trypanosomiasis, Animal African trypanosomiasis, Cattle, Zoonoses, One Health, Mathematical modelin

The effect of weather and climate on dengue outbreak risk in Peru, 2000-2018: A time-series analysis.

BackgroundDengue fever is the most common arboviral disease in humans, with an estimated 50-100 million annual infections worldwide. Dengue fever cases have increased substantially in the past four decades, driven largely by anthropogenic factors including climate change. More than half the population of Peru is at risk of dengue infection and due to its geography, Peru is also particularly sensitive to the effects of El Niño Southern Oscillation (ENSO). Determining the effect of ENSO on the risk for dengue outbreaks is of particular public health relevance and may also be applicable to other Aedes-vectored viruses.MethodsWe conducted a time-series analysis at the level of the district-month, using surveillance data collected from January 2000 to September 2018 from all districts with a mean elevation suitable to survival of the mosquito vector (ResultsWe detected a positive and significant effect of temperature (°C, RR 1.14, 95% CI 1.13, 1.15, adjusted for precipitation) and ENSO (ICEN index: RR 1.17, 95% CI 1.15, 1.20; ONI index: RR 1.04, 95% CI 1.02, 1.07) on outbreak risk, but no evidence of a strong effect for precipitation after adjustment for temperature. Both natural region and season were found to be significant effect modifiers of the ENSO-dengue effect, with the effect of ENSO being stronger in the summer and the Selva Alta and Costa regions, compared with winter and Selva Baja and Sierra regions.ConclusionsOur results provide strong evidence that temperature and ENSO have significant effects on dengue outbreaks in Peru, however these results interact with region and season, and are stronger for local ENSO impacts than remote ENSO impacts. These findings support optimization of a dengue early warning system based on local weather and climate monitoring, including where and when to deploy such a system and parameterization of ENSO events, and provide high-precision effect estimates for future climate and dengue modeling efforts