Fatal coinfection of blastocystosis and intestinal trichomoniasis in a rhesus macaque (Macaca mulatta)

A 3-year-old male rhesus macaque was presented at Referral Veterinary Polyclinic-Teaching Veterinary Clinical Complex, with a chief complaint of chronic diarrhoea and swelling of dependent body parts. The patient's history indicates that the monkey had been experiencing diarrhoea for the past month, with 2–3 episodes of vomiting in the last 2 days. Additionally, oedema has developed within the last 2 weeks. The clinical examination findings revealed dullness and depression, the mucus membrane appeared pale, with a temperature-102.1 °F, a respiration rate-28/min, and a heart rate-92/min. The capillary refill time was 4 s. During the physical examination, the animal exhibited oedema on the dependent part of the body and faecal staining around the perineum along with loose yellow stool. Direct saline and iodine mount faecal smear examination revealed the presence of many motile pear-shaped flagellated protozoa and round vacuolated Blastocystis organisms. Giemsa-stained faecal smear cytology confirmed the presence of Pentatrichomonas sp. and Blastocystis sp. along with many microbes. The faecal culture was negative for all pathogenic microbes. The case was diagnosed as co-infection Blastocystosis and intestinal trichomoniasis. The treatment was initiated with a combination of sulfamethoxazole + trimethoprim @ 35 mg/kg body weight and metronidazole @25 mg/kg administered orally once daily for 7 days. Supportive therapy includes hematinic injection (iron sorbitol, folic acid and vitamin B12) @ 1 ml total dose, administered intramuscularly on alternate days for four occasions as well as intravenous infusion of crystalline amino acid @ 5 ml total dose on alternate days for four occasions. To manage vomition, injection ondansetron was administered@0.5 mg/kg intramuscularly, twice daily for 3 days and H2 blockers, including injection ranitidine@2 mg/kg intramuscularly twice daily for 3 days. Electrolyte and probiotic supplementation were administered orally. After 7 days of therapy, the oedema had significantly improved and episodes of vomition were stopped but there was no significant improvement in the episode of diarrhoea and consistency of faeces. Unfortunately, on the 10th day of therapy, the animal suddenly collapsed. Understanding the virulence pattern of opportunistic protozoa in primates is crucial, and identifying suitable therapeutic candidates to prevent fatal outcomes is the need of the hour, especially considering protozoal infections as an important differential diagnosis in gastrointestinal tract-related ailments. Our study successfully demonstrated the co-occurrence of blastocystosis and intestinal trichomoniasis, both uncommon infections with potential zoonotic implications. © Indian Society for Parasitology 2024.