First report of Hydatigera kamiyai infection in a crowned sifaka (Propithecus coronatus): clinical presentation, parasite identification and implications for zoological collections

Only 14 crowned sifaka (Propithecus coronatus), a critically endangered lemur species, are currently held in zoological institutions. Hydatigera kamiyai is a newly described cryptic species within the Hydatigera taeniaeformis complex. A 3-year-old crowned sifaka presented with acute right hemiparesis. Magnetic resonance imaging exam revealed a two-centimetre diameter left thalamic mass with severe oedema, suggestive of an abscess. Intravenous antimicrobial therapy was initiated with metronidazole and trimethoprim-sulfamethoxypyridazine and continued for one month, as blood culture results were inconclusive. Clinical follow-up included unremarkable complete blood work and repeated MRI exams. The latter revealed an 80% reduction in the size of the mass, associated with full clinical recovery within 60 days. Because some tapeworms, such as Taenia martis, can cause nodular lesions in various locations in humans and non-human primates, a deworming treatment was implemented. Simultaneous immunological testing for hydatidosis and cysticercosis was strongly positive (ELISA, serum immunoglobulin G: 1.741). Oral praziquantel at 25 mg/kg led to severe lethargy after a single dose. Abdominal ultrasound under volatile general anaesthesia revealed two three-centimetre diameter heterogeneous hepatic cavitary structures containing linear hyperechoic elements, with a 0.8-centimetre-thick wall. Oral deworming treatment was readjusted and consisted in 15 days of praziquantel, followed by one-month of albendazole. Four months following the appearance of the first clinical signs, the animal suddenly became comatose and died despite intensive care. Post-mortem exam revealed multiple 12-centimetre-long pseudosegmented larvae (strobilocerci) within hepatic lesions. Brain histology revealed a resolving chronic abscess inconsistent with a parasitic aetiology. The larvae isolated in the liver were identified as Hydatigera kamiyai through morphological and molecular approaches. This cryptic species, belonging to the Hydatigera genus, most likely uses rodents as intermediate hosts and domestic cats as definitive hosts to complete its life cycle. Based on a thorough literature review, this report is the first description of an infection by this cestode in a non-human primate. Non-human primates may serve as aberrant intermediate hosts for Hydatigera kamiyai, which raises concerns regarding its potential zoonotic risk. This case also underscores the importance of parasitological surveillance in zoological institutions and the relevance of One Health considerations.