PREVALENCE AND MORPHOMETRIC STUDIES ON PORCINE CYSTICERCOSIS IN ADAMAWA STATE, NIGERIA

ABSTRACT

Porcine cysticercosis is a parasitic disease caused by the larval stage of Taenia solium, a tapeworm that affects pigs. It is a zoonotic disease of significant public health concern, as humans can acquire the infection by consuming undercooked pork containing viable cysts. In Nigeria, specifically in Adamawa State, there is limited information on the prevalence and morphometric characteristics of porcine cysticercosis. This knowledge gap hampers the development and implementation of effective control strategies to mitigate the public health risks associated with the disease. This study aims to address this gap by investigating the prevalence and morphometric studies of porcine cysticercosis in Adamawa State, Nigeria. Tongue examination, Postmortem examination and detection of circulating antigen (Ag-ELISA) were used to establish the prevalence of T. solium porcine cysticercosis in pigs. To determine the risk factors associated with transmission of porcine cysticercosis in pigs, a questionnaire was administered. Of the 698 pigs examined on tongue examination, 44 (6.3%) were positive for cysticercosis. On postmortem examination, 4 (18.2%) out of 22 pig carcasses were positive for cysticercosis whereas out of 330 pigs, 110 (33.3%) were positive for cysticercosis by Ag-ELISA. The prevalence on tongue examination by village was 8.7% (29/335), 5.9% (8/135) and 3.1% (7/228) for Diagil, Kwaba and Kwachifa villages, respectively. On tongue examination, Diagil village had significantly higher 8.7% (29/335), (χ² = 7.143, P = 0.021) prevalence of porcine cysticercosis than Kwachifa and Kwaba villages whose prevalence was 3.1% (7/228) and 5.9% (8/135) respectively. On PM inspection, only Kwaba village recorded 4/18 (22.2%) pigs with cysticercosis.Kwaba village had the highest prevalence (70.2%) of porcine cysticercosis on Ag-ELISA compared to Diagil (21.1%) and Kwachifa (51.2%) villages. Like was obtained on tongue examination, prevalence of cysticercosis in pigs on Ag-ELISA showed a statistically significant difference in female pigs 36.7% (98/267, C.I. = 30.92 – 42.48) than males 19.0% (12/63, C.I. = 9.31 to 28.69) and that female pigs were 2.53 times more likely to be infected with cysticercosis than male pigs on Ag-ELISA.  When analysed by age, adult pigs 10.1% (42/417, C.I. = 7.21 – 12.99) had a significantly higher prevalence (OR=15.624, χ2 = 24.902, P < 0.001) of cysticercosis than young pigs 0.7% (2/281, C.I. = -0.27 – 1.67) on tongue examination. However, there was no statistical difference (OR= 0.979 χ2 = 0.000, P = 1.000) on prevalence between adult 33.3% (76/228, C.I. = 27.18 – 39.42) and young 33.3% (34/102, C.I. = 24.15 to 42.45) pigs on Ag-ELISA. Pig management system (confined vs free- range), sex of the pig and the locality (village) were the significant risk factors for porcine cysticercosis based on Ag-ELISA. This study has demonstrated that porcine cysticercosis in prevalent in Adamawa state which implies that there are human tapeworm carriers and thus poses a public health risk. It is therefore recommended that a study be conducted in humans to better understand the epidemiology of T. solium infections in Adamawa state.

 

CHAPTER 1

1.0.      INTRODUCTION

Porcine cysticercosis is a zoonotic parasitic disease caused by the larval stage of Taenia solium, a tapeworm that affects both humans and pigs. Infection occurs when humans consume undercooked pork containing viable cysts or through fecal-oral contamination with eggs shed in the feces of infected individuals. In humans, the infection can lead to neurocysticercosis, a potentially serious condition affecting the central nervous system. Porcine cysticercosis poses a significant public health and economic burden in many parts of the world, particularly in areas where pig husbandry practices are suboptimal and sanitation is poor.

Taenia solium is a significant tapeworm species that causes taeniosis in humans, who serve as the definitive host, and pigs, which act as intermediate hosts. In pigs, the larval stages of T. solium (cysticerci) develop, resulting in a condition known as cysticercosis (Murrell, 2005). However, T. solium can also infect humans, who then become accidental hosts and acquire human cysticercosis. Human infection occurs when undercooked pork contaminated with viable cysticerci is ingested (Murrell, 2005). In humans, T. solium can cause taeniosis as the tapeworm matures and releases proglottids laden with eggs or just eggs in the feces. These eggs are immediately infectious to the intermediate host (Murrell, 2005).

When the cysticerci of T. solium lodge in the brain, it leads to a condition called neurocysticercosis (NCC), which is one of the most significant neurological parasitic diseases in humans and a major preventable cause of acquired epilepsy in endemic areas (Carabin et al., 2011). NCC accounts for approximately 30% of acquired epilepsy cases in developing countries (Ndimubanzi et al., 2010). Therefore, T. solium is of great public health importance (Gajadhar et al., 2006). Infections with adult tapeworms are often asymptomatic, although some individuals may experience abdominal discomfort, nausea, diarrhea, and loss of appetite (Muller, 1975).

Reports of Taenia solium are predominantly found in developing countries in Africa, Asia, and Latin America (Eom et al., 2009). The endemicity of the disease in these countries is associated with factors such as poverty, free-ranging pigs, and poor sanitary conditions, particularly the lack of latrines (Phiri et al., 2003; Murrell, 2005; Sikasunge et al., 2007). Many studies have documented high prevalence rates of T. solium infection in pigs in Africa, with rates reaching as high as 64% (Dorny et al., 2004b; Phiri et al., 2003). The disease complex of cysticercosis/taeniosis remains a neglected tropical disease, and its true burden is still not fully determined (Carabin et al., 2005; Praet et al., 2009). The global burden of T. solium cysticercosis, measured in Disability Adjusted Life Years (DALYs), is estimated to range from 2 to 5 million, which is comparable to other neglected parasitic zoonoses but lower than the “big three” global infectious diseases, namely malaria, HIV, and tuberculosis (Torgerson & Macpherson, 2011). However, this estimate may be an underestimate due to limited available data (Flisser and Gyorkos, 2007). While epidemiological studies have contributed to understanding the endemicity of the disease in some countries like Mexico (Flisser and Gyorkos, 2007), this has not been the case in many endemic countries, particularly those in sub-Saharan Africa.

1.2 STATEMENT OF THE PROBLEM

Porcine cysticercosis is a significant public health concern in many parts of the world, including Nigeria. However, there is limited information about the prevalence and morphometric characteristics of porcine cysticercosis in Adamawa State, Nigeria. This knowledge gap hinders the development and implementation of effective control strategies to mitigate the public health risks associated with the disease. Therefore, the main problem addressed by this research is the lack of comprehensive data on the prevalence and morphometric studies of porcine cysticercosis in Adamawa State, Nigeria.

1.3 RESEARCH QUESTIONS

Specifically, the research aims to address the following questions:

1. What is the prevalence of porcine cysticercosis among pigs slaughtered in selected abattoirs in Adamawa State?
2. What are the morphometric characteristics of cysticerci recovered from infected pigs?
3. Are there any potential risk factors associated with porcine cysticercosis in the study area?

1.4 RESEARCH OBJECTIVES

The general objective of this research is to assess the prevalence and morphometric characteristics of porcine cysticercosis in Adamawa State, Nigeria.

The specific objectives include:

1. a) To determine the prevalence of porcine cysticercosis among pigs slaughtered in selected abattoirs across Adamawa State.
2. b) To identify the morphometric features of cysticerci recovered from infected pigs.
3. c) To investigate potential risk factors associated with porcine cysticercosis in the study area.

1.3 SIGNIFICANCE OF THE STUDY

This research will contribute to the existing knowledge on porcine cysticercosis in Adamawa State, Nigeria. The findings will provide important insights into the prevalence and morphometric characteristics of the disease, which can guide the development of appropriate control strategies. The study will also help raise awareness among pig farmers, abattoir workers, and the general public about the risks associated with porcine cysticercosis and the importance of good husbandry practices, proper meat inspection, and hygiene.

Furthermore, the results of this study can inform policymakers and public health authorities in designing interventions to reduce the burden of porcine cysticercosis and prevent the transmission of neurocysticercosis to humans. By understanding the epidemiology of the disease and identifying potential risk factors, targeted control measures can be implemented to protect both animal and human health.

1.5 SCOPE AND LIMITATIONS

This research will focus on studying the prevalence and morphometric characteristics of porcine cysticercosis in Adamawa State, Nigeria. The study will involve collecting post-mortem data from selected abattoirs within the state and examining cysticerci recovered from infected pigs. However, it is important to note that the study will not cover the clinical aspects of neurocysticercosis in humans.

One of the limitations of this study is the reliance on post-mortem examination for the diagnosis of porcine cysticercosis. This method may underestimate the true prevalence of the disease, as it does not account for pigs that may be infected but do not show visible cysticerci during post-mortem inspection. Additionally, the study will be constrained by logistical and resource limitations, which may affect the sample size and the generalizability of the findings.

 

1.6 DEFINITION OF TERMS

To ensure clarity and understanding, the following key terms used in this research are defined as follows:

Porcine Cysticercosis: A parasitic disease caused by the larval stage of Taenia solium, a tapeworm that affects pigs. It is characterized by the presence of cysticerci (larval cysts) in the muscle tissues of infected pigs.

Prevalence: The proportion of individuals in a population that has a specific condition or disease at a particular point in time. In this study, prevalence refers to the percentage of pigs infected with porcine cysticercosis among those slaughtered in selected abattoirs in Adamawa State.

Morphometric Characteristics: The quantitative measurements and descriptive features used to describe and classify the size, shape, and other physical attributes of cysticerci recovered from infected pigs. This includes measurements such as length, width, and thickness.

Zoonotic Disease: A disease that can be transmitted between animals and humans. Porcine cysticercosis is a zoonotic disease because humans can acquire the infection by consuming undercooked pork containing viable cysts.

Risk Factors: Factors or conditions that increase the likelihood of an individual or population becoming infected with porcine cysticercosis. Examples of potential risk factors include poor sanitation practices, lack of meat inspection, and inadequate pig husbandry practices.

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