Selected Endemic Zoonoses in Pigs Presenting for Slaughter in Kampala, Uganda

Cross-sectional serosurvey of Leptospira species among slaughter pigs, goats, and sheep in Uganda

INTRODUCTION

Leptospira are a group of bacteria, including pathogenic types that cause leptospirosis. In Uganda, Leptospira exposure has been reported in humans, with domesticated animals being speculated as the source. However, comparable evidence of Leptospira prevalence and circulating serovars/serogroups in animals is only documented for cattle, and dogs. Our study determined Leptospira seroprevalence, associated risk factors and serogroups circulating among slaughtered pigs, goats, and sheep in Uganda.

METHODS

During an 11-month cross-sectional survey in selected slaughter facilities in three regions of Uganda, we collected blood from 926 pigs, 347 goats, and 116 sheep. The age, sex, breed, and origin of each sampled animal were noted. The samples were tested for anti-Leptospira antibodies using the microscopic agglutination test, based on a panel of 12 serovars belonging to 12 serogroups.

RESULTS

Leptospira seroprevalence was 26.67% (247/926, 95%CI 23.92-29.61) among pigs, and 21.81% (101/463, 95%CI 18.29-25.80) in goats and sheep (small ruminants). L. interrogans Australis and L. kirschneri Grippotyphosa were the commonest serovars among pigs, as was L. borgpetersenii Tarassovi in small ruminants. Pigs sourced from the Eastern (Odds Ratio [OR] = 2.82, 95%CI 1.84-4.30) and Northern (OR = 3.56, 95%CI 2.52-5.02) regions were more likely to be seropositive, compared to those from the Central region. For small ruminants, being female (OR 2.74, 95% CI 1.69-4.57) and adult (OR 4.47, 95% CI 1.57-18.80) was significantly more associated with Leptospira seropositivity. Conclusion/significance: Detection of a moderate seroprevalence, and several Leptospira serogroups among pigs, sheep, and goats from all regions of Uganda, supports existing reports in cattle and dogs, and implies widespread Leptospira exposure in domestic animals in Uganda. These findings may inform future programs for the control of leptospirosis in livestock in Uganda.

Seroprevalence of Brucella spp. and Rift Valley fever virus among slaughterhouse workers in Isiolo County, northern Kenya

Brucella spp. and Rift Valley fever virus (RVFV) are classified as priority zoonotic agents in Kenya, based on their public health and socioeconomic impact on the country. Data on the pathogen-specific and co-exposure levels is scarce due to limited active surveillance. This study investigated seroprevalence and co-exposure of Brucella spp. and RVFV and associated risk factors among slaughterhouse workers in Isiolo County, northern Kenya. A cross-sectional serosurvey was done in all 19 slaughterhouses in Isiolo County, enrolling 378 participants into the study. The overall seroprevalences for Brucella spp. and RVFV were 40.2% (95% CI: 35.2-45.4) and 18.3% (95% CI: 14.5-22.5), respectively while 10.3% (95% CI 7.4%-13.8%) of individuals were positive for antibodies against both Brucella spp. and RVFV. Virus neutralisation tests (VNT) confirmed anti-RVFV antibodies in 85% of ELISA-positive samples. Our seroprevalence results were comparable to community-level seroprevalences previously reported in the area. Since most of the study participants were not from livestock-keeping households, our findings attribute most of the detected infections to occupational exposure. The high exposure levels indicate slaughterhouse workers are the most at-risk population and there is need for infection, prevention, and control programs among this high-risk group. This is the first VNT confirmation of virus-neutralising antibodies among slaughterhouse workers in Isiolo County and corroborates reports of the area being a high-risk RVFV area as occasioned by previously reported outbreaks. This necessitates sensitization campaigns to enhance awareness of the risks involved and appropriate mitigation measures.

Leptospiral uveitis- "Transition 'from epidemic to endemic form" difficulties in laboratory confirmations

Purpose

Leptospirosis is a waterborne zoonotic disease that primarily causes systemic illness, followed by uveitis. After heavy flooding in Madurai district, an epidemic outbreak of systemic and ocular leptospirosis occurred in 1994. Our data shows a transition to endemicity after each epidemic.

Aim

The aim of this study is to report the clinical signs, epidemic outbreaks, and persistent endemicity of leptospiral uveitis, as well as the diagnostic dilemmas associated with it.

Methods

A retrospective analysis of clinical signs was conducted using medical records of leptospiral uveitis patients over a period of 27 years (1994-2020) in a tertiary care eye hospital. The clinical workup of uveitis included a detailed clinical history, systemic, and ophthalmic examination. Microagglutination tests (MATs) was done at the Centers for Disease Control and Prevention (CDC) in Atlanta and later in our regional laboratory. Serum samples were collected from human systemic leptospirosis cases and a small group of animals in and around Madurai.

Results

The first epidemic outbreak resulted in 200 seropositive patients. Subsequent epidemic outbreaks occurred in 1997, 1998, 2001, 2005, and 2012, with Madurai experiencing multiple outbreaks. However, the disease remained endemic, with 25-50 patients being observed per year in between the peaks. Ocular examination revealed acute non-granulomatous uveitis (94.9%), pan uveitis (59.8%), vitreous inflammatory reaction (55.4%), retinal vasculitis (29.5%), disc hyperemia (20.9%), and hypopyon. (16.2%). New serovars emerged every year, resulting in decreased sensitivity of the MAT. Over time, the MAT started to miss diagnoses.

Conclusion

The persistent endemicity of leptospiral uveitis emphasizes the need for accessible diagnostic tests. The low performance of the MAT can be attributable to the use of an older panel. The incorporation of new isolates in the MAT by a national laboratory will improve the accuracy of diagnosis.

A scoping review of zoonotic parasites and pathogens associated with abattoirs in Eastern Africa and recommendations for abattoirs as disease surveillance sites

Abattoirs are facilities where livestock are slaughtered and are an important aspect in the food production chain. There are several types of abattoirs, which differ in infrastructure and facilities, sanitation and PPE practices, and adherence to regulations. In each abattoir facility, worker exposure to animals and animal products increases their risk of infection from zoonotic pathogens. Backyard abattoirs and slaughter slabs have the highest risk of pathogen transmission because of substandard hygiene practices and minimal infrastructure. These abattoir conditions can often contribute to environmental contamination and may play a significant role in disease outbreaks within communities. To assess further the risk of disease, we conducted a scoping review of parasites and pathogens among livestock and human workers in abattoirs across 13 Eastern African countries, which are hotspots for zoonoses. Our search results (n = 104 articles) showed the presence of bacteria, viruses, fungi, and macroparasites (nematodes, cestodes, etc.) in cattle, goats, sheep, pigs, camels, and poultry. Most articles reported results from cattle, and the most frequent pathogen detected was Mycobacterium bovis, which causes bovine tuberculosis. Some articles included worker survey and questionnaires that suggested how the use of PPE along with proper worker training and safe animal handling practices could reduce disease risk. Based on these findings, we discuss ways to improve abattoir biosafety and increase biosurveillance for disease control and mitigation. Abattoirs are a 'catch all' for pathogens, and by surveying animals at abattoirs, health officials can determine which diseases are prevalent in different regions and which pathogens are most likely transmitted from wildlife to livestock. We suggest a regional approach to biosurveillance, which will improve testing and data gathering for enhanced disease risk mapping and forecasting. Next generation sequencing will be key in identifying a wide range of pathogens, rather than a targeted approach.

Sero-prevalence and factors associated with anti-Brucella antibodies in slaughter livestock in Uganda

Introduction

Brucellosis is endemic in Uganda and is a major cause of production losses in livestock. Early detection and quantification of the disease is vital for its control and eradication. The aim of this study was to assess the sero-prevalence and factors associated with anti-Brucella antibodies in slaughtered livestock.

Materials and methods

Sera from 886 cattle, 925 small ruminants, and 900 pigs were collected from regional abattoirs in Northern, Eastern and Central Uganda. To estimate sero-prevalence, sera were serially tested using a combination of the Rose Bengal Test (RBT) and Native Hapten (NH) immunoprecipitation test. True sero-prevalence was estimated using the Rogan-Gladden estimator considering the sensitivity and specificity of the NH immunoprecipitation test. Multivariable logistic regression was used to assess factors associated with seropositivity for anti-Brucella antibodies.

Results and discussion

Small ruminants showed the highest seroprevalence (6.7%, 95% CI = 4.2-7.1) followed by cattle (3.8%, 95% CI = 2.4-4.9) and pigs (2.8%, 95% CI = 1.1-2.9). Seropositivity for anti-Brucella antibodies was associated with region of origin (OR = 4.6,95%CI=1.49-17.75, p = 0.013) for cattle; sex (OR = 2.90, 95% C = 1.5-6.34, p = 0.004), age (OR=4.04, 95% CI = 1.07-8.52, p = 0.006) and species (OR = 2.53, 95% CI = 1.08-6.98, p = 0.048) for small ruminants; and finally sex for pigs (OR = 2.88, 95% CI = 1.07-8.52, p = 0.041). Progressive control interventions must include both cattle and small ruminants since they play a bigger role in the maintenance and dissemination of Brucella. The interventions should adopt a risk-based approach with regions at higher risk being given top priority. Bacteriological and molecular studies should be undertaken to clarify the role of pigs and the goat-cattle cross infections in the epidemiological cycle of brucellosis in Uganda.

Structure of the pork value chain in Northern Uganda: implications for Taenia solium control interventions

Introduction

This study characterizes the pork value chain in Agago, Kitgum, Lamwo, and Pader districts of Northern Uganda and analyzes its implications on the transmission and control of Taenia solium infections.

Methodology

Data were collected through focus group discussions (FGDs) with farmers and pig and pork traders, key informant interviews (KIIs) with local government officials and consumers, and district-level multi-stakeholder mini workshops organized in the study area. The value chain actors identified include input and services providers, pig farmers, live pig traders, pork traders, and consumers.

Results

Most of the pig production, marketing and consumption was found to occur through informal channels. Pig production in this area is dominated by smallholder extensive systems, with most producers keeping less than 10 pigs. The production segment of the pig value chain is characterized by low use of inputs and services such as veterinary extension, drugs and improved feeds. Pigs scavenge for food under free-range systems and are at risk of parasitic infections such as the zoonotic helminth Taenia solium. This risk is exacerbated by the inherent contextual aspects of the study sites including low latrine coverage, open defecation, and high poverty. In addition, some respondents viewed pigs as "sanitation policemen" where they leave them to roam around and eat dirt including feaces thereby cleaning the environment. T. solium was recognized as an important pig health constraint in this value chain alongside African swine fever (ASF). Unlike ASF that was associated with the pig mortalities, the cysts were associated with rejection of pigs by traders at purchase, condemnation of pig carcasses by meat inspectors and rejection of raw pork by consumers at points of sale.

Discussion

Poor organization of the value chain and lack veterinary extension and meat inspection services results in some pigs infected with T. solium entering the food chain, exposing consumers to infection with the parasite. To reduce the pig production losses and public health impact from T. solium infections, there is need for control and prevention interventions targeting specific nodes of the value chain where the risk of transmission is highest.

Sero-prevalence of anti-Leptospira antibodies and associated risk factors in rural Rwanda: A cross-sectional study

Background

Leptospirosis is a zoonotic disease transmitted through the urine of wild and domestic animals, and is responsible for over 50,000 deaths each year. In East Africa, prevalence varies greatly, from as low as 7% in Kenya to 37% in Somalia. Transmission epidemiology also varies around the world, with research in Nicaragua showing that rodents are the most clinically important, while studies in Egypt and Chile suggest that dogs may play a more important role. There are no published studies of leptospirosis in Rwanda.

Methods & findings

We performed a cross-sectional survey of asymptomatic adults recruited from five occupational categories. Serum samples were tested using ELISA and Microscopic Agglutination Test (MAT). We found that 40.1% (151/377) of asymptomatic adults had been exposed to Leptospira spp. Almost 36.3% of positive subjects reported contact with rats (137/377) which represent 90.7% among positive leptospira serology compared with 48.2% of negative subjects (182/377) which represent 80.5% among negative leptospira serology (OR 2.37, CI 1.25–4.49) and 1.7 fold on prevalence ratio and 2.37 of odd ratio. Furthermore, being a crop farmer was significantly associated with leptospirosis (OR 2.06, CI 1.29–3.28). We identified 6 asymptomatic subjects (1.6%) who met criteria for acute infection.

Conclusions

This study demonstrates a high prevalence of leptospiral antibodies infection among asymptomatic adults in rural Rwanda, particularly relative to neighboring countries. Although positive subjects were more likely to report rat contact, we found no independent association between rats and leptospirosis infection. Nonetheless, exposure was high among crop farmers, which is supportive of the hypothesis that rats together with domestic livestock might contribute to the transmission.

Further studies are needed to understand infecting Leptospira servers and elucidate the transmission epidemiology in Rwanda and identify means of host transmitters.

Leptospirosis is the most widespread zoonosis in the world, and infections are underappreciated in regions of the world where it may be mistaken for malaria and other tropical illnesses. We performed a seroprevalence study of leptospirosis in healthy asymptomatic adults in Rwanda. Among 377 subjects, we found evidence of infection in 40.1% (151 / 377), which is higher than in neighboring countries such as Kenya (7 to 16%), Tanzania (10 to 15.8%) and Uganda (15%). Our data suggest that leptospirosis may be a common cause of febrile illness in Rwanda, but further studies are needed to differentiate active from asymptomatic.