Gross Findings: 

On external examination, the keel is sharp. Large amounts of grainy brown fecal material are present on the feathers surrounding the vent and on the ventral surface of the tail. On internal examination, there is no subcutaneous, visceral, or epicardial fat, and there is marked atrophy of the pectoral muscles. A tumor-like mass composed of massively enlarged, firm, torturous loops of small intestine (distal duodenum and proximal jejunum) is present in the mid-coelom (Fig 1A). Adhesions are present between the small intestine and adjacent coelomic organs. On transversely cut surface, the lumen of the affected small intestine is filled with large white worms surrounded by laminated accretions of necrotic material (Fig 1B). 

Histopathological Findings: 

Sections of the severely thickened small intestine reveal that the lumen is filled with concentric layers of necrotic cellular debris surrounded by palisading macrophages. Within the more organized, chronic necrotic material there are scattered areas of acute necrosis and occasional bacterial colonies (parasite migration tracks) (Fig 1C). Multiple cross-sections of nematode parasites can be seen in sections of the proximal duodenum (Fig 1D). 

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Morphologic Diagnosis: Chronic, severe, segmental necrotizing enteritis with intralesional nematodes. 

Disease: Intestinal nematodiasis.

Etiology: Porrocaecum angusticolle. P. angusticolle is a nematode parasite in the order Ascaridida, family Toxocaridae. 

Distribution: P. angusticolle has a cosmopolitan distribution and appears to exist wherever raptors are present. 

Seasonality: Seasonality has not been specifically reported; however P. angusticolle eggs in the environment hatch into infective larvae when temperatures are in the range of 22-32^o C.

Host range: Raptors, including but not limited to Buteo, Accipiter, Circus, Strigiformes, Aquila, and Haliaeetus species.

Transmission: Raptors are believed to become infected with P. angusticolle through ingestion of intermediate hosts including earthworms, insectivores, and fish. Intermediate hosts contain active larvae, which then develop into adults in the intestine of the terminal host (raptors). Ingestion of the infective larvae may occur when raptors feed on prey species which have ingested infected intermediate hosts.

Clinical signs: Affected birds may show weakness, wasting, and emaciation.

Pathology: Grossly, P. angusticolle nematodes may be seen in the proventriculus, ventriculus, and small intestine. Hemorrhagic and/or necrotizing gastritis and enteritis associated with the presence of adult worms is commonly seen.

Diagnosis: Parasitological examination of nematodes collected from the gastrointestinal tract of infected birds is necessary to determine the species present. Morphologic descriptions of P. angusticolle are detailed in Gui et al (see reference below).

Public health concerns: None currently known.

Wildlife population impacts: The prevalence of disease caused by P. angusticolle in raptors has not been described, and the impact of the parasite on raptor populations is unknown. 

Management: No management strategies have been described at this time.

References:

• Guo N, Sitko J, Chen H, Li L. 2021. Morphological and genetic characterization of Porrocaecum angusticolle (Molin, 1860) (Nematoda: Ascaridomorpha) from the common buzzard Buteo buteo (Linnaeus) (Accipitriformes: Accipitridae) in Czech Republic. Parasitol Intern 83:102365. https://doi.org/10.1016/j.parint.2021.102365.
• Liu G, Liu Q, Zhang W, Shen X. 2023. First reported Porrocaecum angusticolle infection in Griffon vulture (Gyps fulvus) in China. Front Cell Infect Microbiol 13:1181999. https://doi.org/10.3389/fcimb.2023.118999.
• Morgan BB, Schiller EL. 1950. Porrocaecum angusticolle (Nematoda) in North American hawks. Trans Am Microcop Soc 69:371-372. https://doi.org/10.2307/3223132.
• Rossi G, Terracciano G, Gherardi R, Galosi L, Perrucci S. 2021. Parasites, bacteria, and associated pathological changes in the digestive system of diurnal and nocturnal raptors in Central Italy. Pathogens 30:1567. https://doi:10.3390/pathogens10121567. PMID: 34959522; PMCID: PMC8707747.