Empirical Bayes estimation of farm prevalence adjusting for multistage sampling and uncertainty in test performance: a Brucella cross-sectional serostudy in southern Kazakhstan

Camel milk is a neglected source of brucellosis among rural Arab communities

The World Health Organization describes brucellosis as one of the world's leading zoonotic diseases, with the Middle East a global hotspot. Brucella melitensis is endemic among livestock populations in the region, with zoonotic transmission occurring via consumption of raw milk, amongst other routes. Control is largely via vaccination of small ruminant and cattle populations. Due to sociocultural and religious influences camel milk (camelus dromedarius) is widely consumed raw, while milk from other livestock species is largely boiled. To investigate the potential public health impact of Brucella in camels we conduct a cross-sectional study in southern Jordan including 227 herds and 202 livestock-owning households. Here we show daily consumption of raw camel milk is associated with Brucella seropositive status among the study population, ORadj 2.19 (95%CI 1.23-3.94) on multivariable analysis, highlighting the need for socioculturally appropriate control measures; targeted interventions among the camel reservoir being crucial for effective control.

A cross-sectional study of Q fever in Camels: Risk factors for infection, the role of small ruminants and public health implications for desert-dwelling pastoral communities

Q fever represents an important 'neglected zoonosis', with high prevalences recorded across the Middle East region. Among rural desert-dwelling communities in the region, camel milk is largely consumed raw, due to perceptions of dromedaries as a uniquely clean livestock species mentioned in the Qur'an and Islamic hadith, while milk from other livestock species is usually boiled. As a result, camels present a unique public health threat among such communities from milk-borne pathogens, including Coxiella burnetii. In view of this, a cross-sectional study was conducted among dromedary herds in southern Jordan between September 2017 and October 2018, including 404 camels from 121 randomly selected herds. In addition, 510 household members associated with these herds were interviewed regarding potential high-risk practices for zoonotic transmission. Weight adjusted camel population seroprevalence for C. burnetii was 49.6% (95% CI: 44.7-54.5), with evidence of maternally derived immunity in calves ≤6 months old. Adjusted herd-level prevalence was 76.0% (95% CI 72.7-80.2). It was estimated 30.4% (144/477) of individuals consumed raw milk from infected herds monthly or more. Following multivariable logistic regression analysis, seropositive status in camels was found to be associated with increasing age, high herd tick burdens, keeping the herd together throughout the year including when calving, and owning larger (>50) sheep and goat flocks, with goats presenting a higher risk than sheep. Racing camel status was found to be protective. Socioculturally appropriate interventions aimed at raising awareness of potential risks associated with drinking raw camel milk, alongside appropriate livestock management interventions, should be considered.

Disparity in prevalence and predictors of undernutrition in children under five among agricultural, pastoral, and agro-pastoral ecological zones of Karamoja sub-region, Uganda: a cross sectional study

Background

Undernutrition accounts for nearly half of under-five child mortality in developing countries where household nutrition is largely dependent on agriculture. Despite the strong influence of agroecology on agriculture in those countries, limited information exists on whether undernutrition in children under five varies with agro-ecological location.

Methods

Using Karamoja sub-region of Uganda, one of the most food insecure parts of Eastern Africa as a case area, and applying a multi-stage sampling procedure, and a structured questionnaire, this study examined in a comparative manner, the prevalence and predictors of undernutrition in children under five among the agricultural, pastoral, and agro-pastoral ecological zones. Chi-square test and Kruskal-Wallis test were used to establish the disparity in prevalence of undernutrition and household contextual characteristics, respectively. Binary logistic regression was used to determine the predictors of undernutrition in children under five among the three agro-ecological zones. The level of statistical significance was set at p ≤ 0.05.

Results

The prevalence of underweight, stunting, and wasting ranged from 36 to 58% but varied with agroecology in terms of the peak age ranging from 6 to 37 months. Child characteristics, feeding practices, household economic factors, sanitation factors, and caregiver characteristics that predict undernutrition among children under five were identified (p ≤ 0.05). Caregiver handwashing after using latrine (p = 0.005) and diarrhoea in a fortnight (p < 0.001) increased the likelihood of stunting in pastoral agroecology only whereas cereal storage in both sacks and granary in agro-pastoral zone was associated with reduced likelihood of both underweight (p < 0.001 and p = 0.014) and stunting (p = 0.011 and p = 0.018), respectively. A male child was more likely to be underweight and stunted in pastoral (p = 0.002 and p = 0.011) and agro-pastoral (p = 0.017 and p = 0.002) agroecology, respectively. Household expenses reduced the likelihood of both underweight and wasting in pastoral (p = 0.013 and p = 0.005) and agricultural (p = 0.011 and p = 0.021) agroecology, respectively. Flour storage duration increased the stunting likelihood in pastoral (p = 0.032) and agro-pastoral (p = 0.006) agroecologies.

Conclusion

This study has revealed that, in a food insecure developing country setting such as Karamoja sub-region of Uganda, undernutrition among children under five varies with agroecology. Thus, nutritional interventions in such locations should be agroecology specific.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03363-6.

Seroprevalence of Toxoplasma gondii in pregnant women and livestock in the mainland of China: a systematic review and hierarchical meta-analysis

Primary Toxoplasma gondii infection in pregnant women may result in abortion, stillbirth, or lifelong disabilities of the unborn child. One of the main transmission routes to humans is consumption of raw or undercooked meat containing T. gondii tissue cysts. We aim to determine and compare the regional distribution of T. gondii seroprevalence in pregnant women and meat-producing livestock in China through a systematic literature review. A total of 272 eligible publications were identified from Medline, Scopus, Embase and China National Knowledge Infrastructure. Apparent and true seroprevalence were analysed by region using a novel Bayesian hierarchical model that allowed incorporating sensitivity and specificity of the applied serological assays. The true seroprevalence of T. gondii in pregnant women was 5.0% or less in seven regions of China. The median of the regional true seroprevalences in pigs (24%) was significantly higher than in cattle (9.5%), but it was not significantly higher than in chickens (20%) and small ruminants (20%). This study represents the first use of a Bayesian hierarchical model to obtain regional true seroprevalence. These results, in combination with meat consumption data, can be used to better understand the contribution of meat-producing animals to human T. gondii infection in China.

Cross-Sectional Study of Toxoplasma gondii Infection in Pig Farms in England

Ingestion of undercooked meat has been proposed as an important source of human Toxoplasma gondii infection. To ascertain the contribution of meat consumption to the risk of human infection, estimates of the prevalence of infection in meat-producing animals are required. A cross-sectional study was conducted to assess T. gondii infection in pigs raised in England, to identify risk factors for infection, and to compare performance of two serological tests: modified agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA). Blood samples from 2071 slaughter pigs originating from 131 farms were collected and 75 (3.6%) were found to be positive by MAT. Positive pigs originated from 24 farms. A subset of samples (n = 492) were tested using ELISA, and a significant disagreement (p < 0.001) was found between the two tests. An empirical Bayes approach was used to estimate the farm-level prevalence and the probability of each individual farm having at least one positive animal, considering the uncertainty arising from the sampling strategy and the imperfect test performance. The adjusted farm-level prevalence was 11.5% (95% credible interval of positive farms 8.4-16.0%). Two different criteria were used for classifying farms as infected: (1) ≥50% probability of having at least one infected pig (n = 5, 6.8%) and (2) ≥10% probability (n = 15, 20.5%). Data on putative risk factors were obtained for 73 farms. Using a 10% cutoff, the relative risk (RR) of infection was higher in farms where cats have direct access to pigs' food (RR = 2.6; p = 0.04), pigs have outdoor access (RR = 3.0; p = 0.04), and farms keeping ≤200 pigs (RR = 3.9; p = 0.02), with strong collinearity between the three variables. The findings suggest a low level of T. gondii infection in the farms studied, most of which are likely to send to slaughter batches comprising 100% uninfected pigs. These results provide key inputs to quantitatively assess the T. gondii risk posed by pork to consumers.