Gastroenteritis Diagnosed at Necropsy: A Review of Cases Spanning a Decade

INTRODUCTION

Gastroenteritis in animals is a prevalent and multifaceted condition characterized by inflammation of the gastrointestinal tract (GIT).^[1,2] It affects a wide range of species, including domestic animals such as dogs, cats, cattle, pigs, and poultry, as well as wildlife. The causes of gastroenteritis can be infectious or non-infectious.^[2-4] Infectious gastroenteritis in animals is often caused by several pathogens, with bacteria such as Escherichia coli, Salmonella, Campylobacter, and Clostridium perfringens commonly implicated.^[5-8] Viruses such as canine parvovirus, feline panleukopenia virus, rotavirus, and coronavirus also play significant roles, particularly in young animals.^[9] Parasitic gastroenteritis (PGE) can result from infestations with protozoans such as Giardia and Cryptosporidium or helminths such as roundworms, hookworms, and tapeworms.^[10] In addition, non-infectious factors such as dietary changes, ingestion of foreign bodies, toxins, stress, and underlying systemic diseases can trigger gastroenteritis reactions.^[11,12]

The clinical presentations of gastroenteritis include vomiting, diarrhea, abdominal pain, anorexia, lethargy, and dehydration.^[1] These clinical presentations and severity of gastroenteritis tend to vary greatly with factors such as the underlying cause, species, age, immune status, and environmental conditions.^[13] The gross pathological changes associated with gastroenteritis include signs of inflammation such as redness, swelling, and increased vascularity in the affected tissues.^[14,15] The mucosal lining of the GIT may appear thickened, hyperemic, and friable, with erosions, ulcers, or petechial hemorrhages observed in severe cases.^[16] In addition, there may be an accumulation of mucus, fibrin, and inflammatory exudates within the lumen of the intestine.^[17] On histopathology, gastroenteritis is characterized by several inflammatory lesions affecting the mucosal, submucosal, and, occasionally, the muscular layers of the GIT. These involve epithelial damage, loss of epithelial integrity, and infiltration of inflammatory cells such as neutrophils, lymphocytes, and plasma cells within the lamina propria. Edema, congestion, and hemorrhage may be observed in the submucosal layer. In chronic cases, there may be mucosal regeneration, including epithelial hyperplasia, crypt distortion, and fibrosis.^[18,19]

The diagnosis of gastroenteritis involves a combination of clinical evaluation, laboratory tests, and diagnostic imaging in the live animals, and postmortem examination in the dead animals.^[20] Findings from physical examinations such as abdominal pain, dehydration, and abnormal fecal consistency provide initial clues, which are further supported by laboratory analyses as well as necropsy.^[21]

Necropsy, or postmortem examination, plays a crucial role in assessing the pathological changes associated with gastroenteritis in animals.^[22,23] During necropsy, the GIT is examined to identify gross lesions, thus providing valuable insights into the extent and severity of gastrointestinal involvement.^[24] In addition, histopathological examination of tissue samples obtained during necropsy enables the detailed characterization of inflammatory processes, which contribute to the development and progression of gastroenteritis.^[25] Despite its importance, there is a notable gap in comprehensive data regarding gastroenteritis cases diagnosed at the Necropsy Unit of the Veterinary Teaching Hospital (VTH) at Ahmadu Bello University (A.B.U.) in Zaria, Kaduna State, Nigeria, from 2013 to 2023. This retrospective study seeks to address this gap by examining the prevalence, temporal trends, species, sex, and age-specific distributions associated with gastroenteritis in the local animal population.

MATERIAL AND METHODS

RESULTS

Overall prevalence and yearly distribution of gastroenteritis

From 2013 to 2023, a total of 1052 carcasses were presented to the Necropsy Unit, and gastroenteritis was diagnosed in 20.5% of the carcasses [Table 1].

Table 1: Retrospective data of gastroenteritis diagnosed, from 2013 – 2023, at the Necropsy Unit of the Veterinary Teaching Hospital, Ahmadu Bello University Zaria.

Year	Total number of carcasses presented	Frequency of gastroenteritis diagnosed	Proportion (%)
2013	105	23	21.9
2014	105	17	16.2
2015	193	19	9.8
2016	128	13	10.2
2017	102	36	35.3
2018	107	31	29.0
2019	128	28	21.9
2020	44	10	22.7
2021	64	16	25.0
2022	36	7	19.4
2023	40	16	40.0
Overall	1052	216	20.5

Gastroenteritis was highest (16.7%) in 2017, followed by in 2018 (14.4%) and 2019 (13.0%), and least in 2022 (3.2%) [Figure 1]. The proportions of gastroenteritis were 10.6%, 7.9%, 8.8%, and 6.0% in 2013, 2014, 2015, and 2016, respectively. In 2021 and 2023, the proportions of gastroenteritis were each 7.4%, and 4.6% in 2020 [Figure 1].

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Figure 1:

Yearly trend of gastroenteritis diagnosed, from 2013 – 2023, at the Necropsy Unit of the Veterinary Teaching Hospital, Ahmadu Bello University Zaria.

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Species, sex, and age distributions

The proportion of gastroenteritis was highest (46.3%) in canine, followed by caprine (31.5%) and ovine (8.3%), and least (0.5%) in the antelope, gopherus, lagomorpha, porcine, and snake [Figure 2]. Other species of animals in which gastroenteritis was diagnosed were bovine (3.2%), equine (2.8%), feline (1.4%), and lapine (4.2%) [Figure 2].

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Figure 2:

Distribution of gastroenteritis, based on species of animals, diagnosed from 2013 – 2023 at the Necropsy Unit of the Veterinary Teaching Hospital, Ahmadu Bello University Zaria.

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The proportion of gastroenteritis diagnosed was 100.0% in the males of antelope and porcine; and females of gopherus, lagomorpha, and snake [Figure 3]. Higher proportions of gastroenteritis were diagnosed in the males of canine (51.0%), equine (66.7%), and feline (66.7%), but in the females of bovine (71.4%), caprine (66.2%), lapine (55.6%), and ovine (55.6%) [Figure 3]. There was no significant (P > 0.05) association between the sex and species of animals in which gastroenteritis was diagnosed.

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Figure 3:

Distribution of gastroenteritis, based on sex of animals, diagnosed from 2013 – 2023 at the Necropsy Unit of the Veterinary Teaching Hospital, Ahmadu Bello University Zaria. χ² = 12.261, P = 0.344.

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Gastroenteritis was diagnosed in 100.0% of porcine <1 year; antelope, gopherus, and lagomorpha 1–3 years; and snake >3 years old [Figure 4]. There were higher proportions of gastroenteritis in canine (44.0%), lapine (55.6%), and ovine (44.4%) <1 year; bovine (42.9%) and caprine (50.0%) 1–3 years; and in equine (66.7%) >3 years old [Figure 4]. A significant (P < 0.05) association existed between the age and species of animals diagnosed with gastroenteritis.

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Figure 4:

Distribution of gastroenteritis, based on age of animals, diagnosed from 2013 – 2023 at the Necropsy Unit of the Veterinary Teaching Hospital, Ahmadu Bello University Zaria. χ² = 35.614, P = 0.033.

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DISCUSSION

The overall prevalence of gastroenteritis diagnosed in this study (20.5%) is consistent with the significant burden of gastrointestinal diseases reported in veterinary pathology. The previous studies have documented the widespread occurrence of gastroenteritis in animals, with varied prevalence rates depending on factors such as geographic location, species, and study design. For instance, a study by Shima et al.^[26] reported a gastroenteritis prevalence of 41.2% among sick dogs following a 1-year retrospective medical records of dogs from 10 veterinary clinics in Nigeria. Kataria et al.^[13] reported a 12.2% gastroenteritis prevalence in dogs in India. In a goat, severe PGE was reported.^[27] In another study, the prevalence of GIT parasites reported in buffaloes and cattle was 58.59% in Pakistan.^[28] These observed occurrences emphasize the importance of gastroenteritis as a common pathological condition affecting different species of animals.

The yearly distribution of gastroenteritis cases revealed temporal variations in disease prevalence over the study period, with peaks observed in certain years, such as 2017, 2018, and 2019. These findings align with previous studies that have reported seasonal and annual fluctuations in the incidence of gastrointestinal diseases in animals.^[29-32] Factors such as changes in environmental conditions, management practices, and the introduction of infectious agents might have contributed to the observed fluctuations in gastroenteritis prevalence over time.^{[13,30,33,34]} However, there is a need for further investigation into the specific factors influencing these temporal trends to enhance our understanding of disease dynamics, so as to inform targeted preventive measures.

The species distribution of gastroenteritis in this study highlighted variations in susceptibility among different animal species, with canines, caprines, and ovines identified as the most commonly affected species. This finding is consistent with previous studies that have reported species-specific differences in the prevalence of gastroenteritis.^[33,35,36] The observed species distribution may reflect differences in host susceptibility, environmental exposures, and pathogen reservoirs among animal populations. Furthermore, differences in dietary habits, management practices, and genetic predispositions may also contribute to species-specific variations in gastroenteritis prevalence.^{[19,33,36-38]}

The sex distribution of gastroenteritis cases reveals variations in disease prevalence between male and female animals within certain species. While no significant association was found between sex and species in which gastroenteritis was diagnosed, differences in prevalence between males and females were evident in specific species such as canines, equines, and bovines. These findings are consistent with studies that have reported sex-based disparities in the prevalence of gastrointestinal diseases in animals. Hormonal differences, behavioral factors, and physiological variations between male and female animals may contribute to differences in disease susceptibility and severity.^[39-41]

In the present study, the age distribution of gastroenteritis showed age-related patterns in disease occurrence, with varying prevalence rates observed across different age groups. Young animals, particularly those <1 year old, exhibited higher prevalence rates of gastroenteritis compared to older age groups. Conversely, older animals, particularly those over 3 years old, also exhibited elevated prevalence rates of gastroenteritis. These findings are consistent with studies that have reported age-specific patterns in the prevalence of gastrointestinal diseases in animals.^[33,42] For example, a study on the age distribution of gastroenteritis in dogs found that dogs under 1 year of age were more likely to be infected with multiple viruses compared to older dogs.^[13] Factors such as immature immune systems, nutritional status, and exposure to pathogens may contribute to increased susceptibility to gastroenteritis in young animals, while age-related changes in immune function and gastrointestinal health may predispose older animals to the disease.^[1] However, further research is needed to understand the complex interplay of these factors and their impact on the prevalence of gastroenteritis in different age groups of animals.

CONCLUSION

The findings of this study contribute to our understanding of the epidemiology of gastroenteritis in carcasses presented for postmortem examination at the Necropsy Unit of the VTH, A.B.U. Zaria, and highlight the complex interplay of factors influencing its occurrence and distribution. By identifying temporal trends, species-specific differences, sex-based disparities, and age-related patterns in gastroenteritis prevalence, this study provides valuable insights that can inform targeted interventions for disease prevention, management, and control.