Pathological features of gastrointestinal and hepatobiliary parasitosis in neotropical primates in Northeast Brazil

Silva, Raquel A.F.; Lima, Telma S.; Dias, Rômulo F.F.; Santos, Nayadjala T.A.; Oliveira, Rafael L.; Oliveira, Jaqueline B.; Araújo, Jeann L.; Lucena, Ricardo B.

doi:10.1590/1678-5150-PVB-7301

ABSTRACT:

Understanding primate helminth fauna through the characterization of the associated diseases and parasitism, clinicopathological behavior, and parasite-host relationship is crucial in determining the impact of parasitic infections on free-living and captive species. The present study aimed to describe the primary clinical and anatomopathological aspects of parasitism in non-human primates (NHP). Necropsy records of NHPs diagnosed with endoparasitosis at the Veterinary Pathology Laboratory of the “Universidade Federal da Paraíba” were reviewed to obtain epidemiological, clinical, and pathological data, while samples were collected for parasitological identification at the time of necropsy. All animals were obtained from the cities of Cabedelo and João Pessoa, Paraíba, Brazil, from screening and monitoring centers for animals seized from illegal trafficking in this state. Twenty-four cases of gastrointestinal and hepatobiliary parasites affecting primate species belonging to species of the Sapajus and Callithrix genera were identified. In contrast, Molineus torulosus was identified in the intestinal serosa of 16 animals. Further, there were five cases of Trypanoxyuris callithrix, two cases of Platynosomum illiciens infection, and one case of Dipetalonema gracile. The clinical and pathological behaviors of these diseases ranged from asymptomatic infections, considered based on necropsy findings in 14 cases, to cases with characteristic clinical manifestations associated with the cause of death of the animals in 10 of the 24 cases. Identification of the clinical behavior and pattern of pathological lesions can contribute to a better understanding of the parasite-host relationship and aid in the adequate diagnosis of these diseases.

INDEX TERMS:
Gastrointestinal tract; wildlife; Molineus torulosus; Trypanoxyuris callithrix; Platynosomum illiciens; Dipetalonema gracile

RESUMO:

Compreender a helmintofauna de primatas através da caracterização dessas enfermidades/parasitismos, conhecendo o comportamento clínico-patológico, bem como a relação parasito-hospedeiro é crucial para a determinação do impacto das infecções parasitárias em espécies de vida livre e de cativeiro. Diante disso, o objetivo deste trabalho é descrever os principais aspectos clínicos e anatomopatológicos em casos de parasitismos em primatas não humanos (PNH). Foram revisados os registos de necropsias de primatas diagnosticados com endoparasitoses no Laboratório de Patologia Veterinária da Universidade Federal da Paraíba, para obtenção de dados epidemiológicos, clínicos e patológicos, bem como coletado amostras para identificação parasitológica no momento da necropsia. Os animais vieram dos municípios de Cabedelo e João Pessoa, Paraíba, Brasil, de centros de triagem e monitoramento de animais apreendidos no tráfico ilegal no estado. São relatados 24 casos de parasitoses gastrointestinais e hepatobiliares acometendo espécies de primatas pertencentes aos gêneros Sapajus sp. e Callithrix sp., nos quais foram identificados Molineus torulosus na serosa intestinal de 16 animais. Cinco casos de infecção por Trypanoxyuris callithrix, dois casos de infecção por Platynosomum illiciens e um caso de Dipetalonema gracile. O comportamento clínico e patológico dessas enfermidades variou de infecções assintomáticas sendo considerados achados de necropsia em 14 casos, a casos com manifestações clínicas características associada a causa morte dos animais, representando 10 dos 24 casos totalizados. A identificação do comportamento clínico e padrão de lesões patológicas podem colaborar para melhor entendimento da relação parasito e hospedeiro, além de ajudar no diagnóstico adequado dessas enfermidades.

TERMOS DE INDEXAÇÃO:
Trato gastrointestinal; animais selvagens; Molineus torulosus; Trypanoxyuris callithrix; Platynosomum illiciens; Dipetalonema gracile

Introduction

Endoparasitosis is a clinicopathological condition that shows considerable variability in wild animals, with many non-specific clinical manifestations that may lead to death (Silva et al. 2012, Mattioli et al. 2016). Several studies conducted in Brazil have aimed to identify the helminth fauna of non-human primates (NHP), reporting approximately 50 parasitic helminth species (Corrêa et al. 2016, Figueiredo et al. 2020). However, this number is believed to be underestimated, as the helminth fauna of most Brazilian NHP remains unknown (Corrêa et al. 2016), particularly in the Northeast region of Brazil.

In Brazil, infections by nematodes belonging to the families Molineidae, Oxyuridae, and Onchocercidae, as well as trematodes of the family Dicrocoeliidae, can infect neotropical primates. Particular species include Molineus torulosus, Trypanoxyuris callithrix, Platynosomum illiciens, and Dipetalonema gracile. These species parasitize the intestine, liver, and abdominal cavity and can cause severe gastrointestinal disorders and/or act as susceptibility factors for other diseases (Miguel et al. 2013, Pinto et al. 2013, Mati et al. 2021, Ramalho et al. 2022).

In this context, the study of parasitic infections in wild species is crucial for understanding aspects of the parasite-host interactions, such as transmission routes and zoonotic potential, particularly among NHP in contact with domestic communities (Daszak et al. 2000, Thompson et al. 2010, Klaus et al. 2017). Therefore, this study aimed to describe the pathological aspects of gastrointestinal and hepatobiliary parasites in primates collected from the state of Paraíba in Northeast Brazil.

Materials and Methods

Ethical approval. This study did not involve any animal experiments, as all data were obtained from a review of necropsy record. As such, this manuscript did not need to be submitted to an Animal Ethics Committee (CEUA).

The necropsy records of non-human primates diagnosed with endoparasitosis at the “Laboratório de Patologia Veterinária” of the “Universidade Federal da Paraíba” (LPV/UFPB) from January 2013 to December 2019 were reviewed. Information related to the species, sex, age, and provenance of the animals was subsequently extracted from records. In addition to epidemiological data, information related to the clinical presentation of the affected animals, necropsy findings, and microscopic findings were collected. Furthermore, new necropsy cases in NHP were monitored to identify diseases caused by parasites and parasitism in these animals. New histological slides were prepared from tissues embedded in paraffin or materials preserved in 10% buffered formalin and routinely stained with hematoxylin and eosin (HE) when necessary.

Parasites were collected from the affected anatomical sites, photographed, preserved in a solution of alcohol, formalin, and glacial acetic acid (AFA), and subsequently sent for identification to the “Laboratório de Parasitologia” of the “Universidade Federal Rural de Pernambuco” (LAPAR/UFRPE). According to Anderson et al. (2009), nematodes can be identified at the genus level. In the case of older samples, when buffered formalin material is unavailable, parasite identification can be performed based on photographic records, along with the descriptions in the reports and reference to more current cases.

Results

Throughout the study period, 70 necropsy cases of neotropical non-human primates were recorded at the LPV/UFPB, of which 24 (34.3%) were recorded as having endoparasitism of the gastrointestinal and hepatobiliary tracts. These animals had disparate origins, ranging from captive animals in zoos to animals rescued by wildlife trafficking. In some cases, the animals were found sick in the wild and referred for treatment to a Veterinary Hospital. Of the 24 identified cases, 17 were diagnosed with Sapajus libidinosus, Sapajus flavius, and Sapajus apella (70.8%), and seven with Callithrix jacchus (29.2%). Overall, endoparasitism occurred predominantly in adults (20/24) and females (11/24). From some records, it was not possible to extract information regarding sex or age.

After parasite identification, 16 cases were attributed to Molineus torulosus infection (66.7%), five to Trypanoxyuris callithrix (20.8%), two to Platynosomum illiciens (8.3%), and one to Dipetalonema gracile (4.2%). The species of affected animals, parasite species, anatomical location, and macroscopic and microscopic alterations are presented in Table 1.

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Table 1.
Characterization of affected animals, parasites, anatomical location, and morphological description of parasitic infections diagnosed in non-human primates at LPV/UFPB, Paraíba, Brazil

Molineus torulosus

Overall, 16 cases of parasitosis were attributed to infection by Molineus torulosus, many of which were from individuals from the Cebidae family. Among these, 11 were reported by Bacalhao et al. (2016). Ten cases occurred in S. libidinosus (yellow-breasted capuchin monkeys), four in S. flavius (golden capuchin monkeys), and two in S. apella (Guianan capuchin monkeys), with nine cases in males and seven in females, with animals ranging in age from juveniles (two cases) to adults (14 cases). All animals came from the municipalities of Cabedelo and João Pessoa, Paraíba, Brazil, originating from screening and monitoring centers for animals seized from illegal trafficking in the state. Clinically, parasitized animals exhibit weight loss that progresses to severe cachexia, apathy, and dehydration.

Macroscopic observations included pronounced emaciation and multifocal to coalescing firm, brownish-gray nodules ranging in diameter from 0.5 to 2.0cm, located in the serosa of the duodenum, proximal third of the jejunum, and pancreas (Fig.1). Upon sectioning, the walls of these nodules were found to be thick and firm, with an irregular and friable central area characteristic of necrosis and mineralization. Occasionally, they were associated with numerous yellowish-white fine cylindrical structures, morphologically suggestive of nematodes such as M. torulosus (Fig.2 and 3). In some sections of the intestine, continuity between these nodules and the intestinal lumen was observed, which was associated with mucosal ulcers. In all cases, respiratory system involvement was observed to varying degrees of severity. The lesions comprised shiny lungs characterized by the presence of amorphous and hyaline material within the alveoli, both macroscopically and microscopically, compatible with pulmonary edema. Irregular and multifocal reddened areas were further distributed throughout the cranial and caudal lobes.

Fig.1-4.
Molineus torulosus infection in Sapajus flavius (golden saguis) and Sapajus apella (Guiana saguis). (1) In the small intestine, the presence of firm, reddish nodules varying in diameter from 0.5 to 2cm. (2) The cut surface of these nodules was thick and firm, with an irregular and friable central area, indicative of necrosis and mineralization. Occasionally, these lesions were associated with numerous filamentous, yellowish-white structures indicative of M. torulosus. (3) Macroscopically visualization of M. torulosus specimens. (4) In the small intestine, longitudinal and transverse sections of the nematodes reveal a thick cuticle (5µm), uniformly spaced longitudinal cuticular ridges, as well as a pseudocoelom, platyhelminth/celomic musculature, and a prominent digestive tract, lined with few multinucleated cells with a brush border. HE, bar = 50µm.

Microscopically, a neutrophilic inflammatory infiltrate associated with myriad bacteria, characteristic of bacterial pneumonia, was observed. Microscopically, parasitic granulomas were observed in the duodenum, between the serosal and muscular layers, occasionally extending to the other layers (transmural). The granulomas were characterized by a necrotic center associated with an inflammatory infiltrate comprising numerous epithelioid macrophages, eosinophils, and neutrophils, as well as multiple cross-sections and longitudinal sections of nematodes compatible with M. torulosus. The nematodes measured up to 120μm and had a cuticle 5μm thick, with uniformly spaced longitudinal cuticular ridges, pseudocoelom, platyhelminth/coelomate musculature, and a prominent digestive tract lined by few multinucleated cells with a brush border (Fig.4). Inside, eggs measuring 30-50μm in diameter with a thin shell were also observed. Lymphocytes and plasma cells surrounded by discontinuous fibrous capsules were further identified.

Small openings communicating with the granulomas and extending to the ulcerated areas in the intestinal mucosa were observed. Neutrophilic and lymphocytic periductal pancreatitis was observed in the pancreases of four animals, with intraductal nematodes and eggs associated with mild desquamation and necrosis of the pancreatic ductal epithelium. Lymphocytes and plasma cells were further observed in the mesentery, with lymphadenitis and invasion of the mesenteric vessels inducing fibrin thrombi in some cases.

Trypanoxyuris callithrix

Five specimens of C. jacchus (white-tufted marmosets) were diagnosed with T. callithrix. All were adults, and three of five were females. All specimens originated from the municipalities of João Pessoa and Areia, Paraíba, Brazil. Clinically, the animals appeared cachectic, with pale mucous membranes, dull and brittle fur, and pronounced eyeball retraction, indicative of severe dehydration (Fig.5). Necropsy findings included distended intestinal loops in the cecum and colon segments, with multiple whitish nematodes present in the intestinal lumen, measuring 2 to 6mm in length; upon opening the segments, moderate reddening of the mucosa was noted (Fig.6).

Fig.5-6.
Trypanoxyuris callithrix in Callithrix jacchus (white-tufted-ear marmosets). (5) A cachectic animal. (6) Segments of the cecum and colon show marked distension of the loops associated with multiple whitish nematodes in the intestinal lumen, measuring 2-6mm in length, with moderately reddened mucosa.

The histopathological findings were characterized by diffuse and moderate inflammatory infiltrates in the mucosal layer of the cecum and colon, comprising lymphocytes, plasma cells, and eosinophils, in addition to moderate edema. Parasites were not observed in histological sections.

Platynosomum illiciens

Two not previously reported cases of platinosomiasis (P. illiciens) affecting white-tufted marmosets (C. jacchus) from the municipalities of João Pessoa and Belém, Paraíba, Brazil, one male and one female, were also assessed. Clinically, pronounced cachexia was observed in both animals; however, only one further presented with diffuse and severe jaundice (Fig.7). On necropsy, parasites were observed in both animals, but with different parasitic loads. In severely parasitized animals, in addition to a pronounced decrease in adipose tissue and muscle mass, the liver exhibited moderately rounded edges with irregular brownish areas across the entire capsular surface. Sectioning revealed numerous parasites with ellipsoid, flattened, and brownish bodies inside the gallbladder (Fig.8 and 9).

Fig.7-10.
Platynosomum illiciens in Callithrix jacchus (white-tufted-ear marmosets). (7) An example animal showing severe cachexia and jaundice. (8) Numerous parasites with ellipsoid, flattened, and brownish bodies can be observed in the opening of the gallbladder. (9) Morphology of the parasites observed at higher magnification. (10) In the liver, there is moderate periportal lymphoplasmacytic inflammatory infiltrate with bile duct proliferation, fibrous tissue, and cholestasis. HE, bar = 20µm.

Histopathological findings included moderate periportal lymphoplasmacytic inflammatory infiltrates with proliferation of the bile ducts, fibrous tissue, and cholestasis (Fig.10), with no parasite sections observed within the bile ducts.

Dipetalonema gracile

A case of infection by D. gracile was identified in an adult male S. flavius (golden capuchin monkey) from the municipality of Cabedelo, Paraíba, Brazil. Clinically, the animal appeared cachectic, with pronounced eyeball retraction. Macroscopic findings revealed microfilariae in the peritoneal cavity, along with exudate, yellowish fibrin filaments, and fibrous adhesions in the abdominal cavity (Fig.11), which further involved the mesentery and capsular surface of the spleen. Hyperemia and enlargement of the mesenteric lymph nodes were also observed, along with multifocal pinpoint-whitish areas in the splenic parenchyma.

Fig.11-12.
Dipetalonema gracile in Sapajus flavius (golden-handed capuchin monkeys). (11) In the abdominal cavity, a filarial nematode can be observed amidst the fibrinous exudate, yellowish fibrin filaments and fibrous adhesions between the abdominal organs. (12) In the spleen, a pronounced and diffuse inflammatory infiltrate composed of plasmocytes, eosinophils, histiocytes, lymphocytes, and rare multinucleated giant cells can be microscopically observed, associated with microfilariae approximately 125µm in length (arrow). HE, bar = 20µm.

Microscopically, pronounced and diffuse inflammatory infiltrate was observed in the spleen and liver, comprising plasma cells, eosinophils, histiocytes, lymphocytes, and rare multinucleated giant cells, associated with microfilariae approximately 125µm in length (Fig.12). Morphologically, filarial nematodes have long, tapered tails with different sexual dimorphisms. Males have four pairs of preanal papillae and unequal slender spicules, whereas females have a vulva near the esophagus’s glandular portion.

Discussion

In the present study, the diagnosis of endoparasitosis in neotropical non-human primates was established based on necropsy, histopathological, and parasitological findings. Endoparasites commonly infect domestic animals; however, most cases can be treated quickly and efficiently, thanks to the wide range of anti-helminthic protocols available on the market (Jones & Garcia 2018). In contrast, in wild animals, whether living freely or maintained under human care, there is still a lack of information complementing the clinical and pathological profiles of helminthoses, which are often diagnosed at the time of necropsy (Pinto et al. 2013), as observed in the present study.

In general, among the predisposing factors for endoparasitosis, age tends to be an important factor, given the greater susceptibility of young animals to debilitating conditions triggered by a high parasitic load (Miguel et al. 2013). In this study, no age- or sex-linked predisposition was observed, which may be related to the small number of animals evaluated and the lack of information in the record sheets. Furthermore, relatively little information was recorded owing to a lack of knowledge regarding the origin of animals. However, in the study by Kumar et al. (2018), a higher prevalence of gastrointestinal parasitic infections was noted in young animals and females.

In the present study, the exact etiopathogenesis of endoparasitosis was not clear; however, it is believed that its occurrence was associated with a history of capture. Animals taken from their habitats are generally placed in small, overcrowded enclosures with scarce food and inadequate nutrition (Freitas et al. 2014). These conditions trigger stress and result in weakness in the animals. Consequently, symbiotic microorganisms may begin to proliferate, causing severe clinical and pathological conditions, or new infections may develop.

This situation poses a challenge not only from a clinical but also from a pathological standpoint, as the determination of the severity of pathological findings is associated with the clinical profile of animals. However, in cases of debilitating conditions and sudden death, the collection of accurate information is impossible. In the present study, necroscopic evaluation allowed the determination of endoparasitosis as a cause of death in at least seven animals, with infections caused by the studied parasites, while endoparasitosis was only a potential necropsy finding in 17 cases, representing a low percentage. However, parasitic infections can also weaken these animals and predispose them to infection with other pathogens, highlighting the importance of cadaveric evaluation (Miguel et al. 2013).

In studies conducted by Siqueira et al. (2016), animals seized from trafficking operations commonly exhibited a low body score, showing emaciation, apathy, and dry, brittle, and dull skin and fur, similar to observations in the present study. However, this condition is more commonly described in avian species, which represent a higher percentage of trafficked animals (Siqueira et al. 2017).