Strongylidae is a family of strongyle nematodes. Several genera and species have been reported in non-human primates. Two genera are of particular interest: Oesophagostomum and Ternidens (Ternidens deminutus being the main species of interest in this genus). They affect the cecum and colon of a large number of primate species (Cogswell, 2007; Strait et al., 2012).

Epidemiology

Strongylidae may affect amongst others:

• Prosimians, namely Bornean slow lorises (Nycticebus menagensis) (Frias et al., 2018b);
• New World Monkeys like howler monkeys (Alouatta ), wooly monkeys (Lagothrix flavicauda), white-footed tamarins (Saguinus leucopus), white-fronted and black capuchin monkeys (Cebus albifrons and Sapajus nigritus), squirrel monkeys (Saimiri sciureus), and monk sakis (Pithecia monachus) (Rondón et al., 2021);
• Old-World Monkeys, namely macaques (Macaca) and baboons (Papio spp.) (Strait et al., 2012; Calle & Joslin, 2015);
• Apes, notably gorillas (Gorilla) and chimpanzees (Pan spp.) (Medkour et al., 2020).

These parasites have been reported on all continents, Oesophagostomum being more cosmopolitan, whereas Ternidens deminutus is mainly found in Africa and Asia (Cogswell, 2007).

Description

Eggs have the typical morphology of a non-embryonated strongyle egg (oval, with a thick outer membrane and non-parallel lateral sides, and contain a morula). Some additional characteristics are typical to the superfamily but can be difficult to identify. For instance, the morula is dense and contains 8 to 16 blastomeres. Eggs are about 65 µm long and 40 µm large and have two equal poles (Cogswell, 2007).

Differential diagnosis

Differential diagnosis includes all non-embryonated strongyle eggs.

Clinical significance

Clinical signs depend on the genus affecting the animal. Oesophagostomum contaminations are normally asymptomatic but can cause digestive signs in case of massive infections. Ternidens deminutus may cause anemia and digestive signs as well (Strait et al., 2012; Calle & Joslin, 2015).

Prophylaxis and treatment

As strongylidae infections may be zoonotic, hygienic measures need to be taken in case of diagnosis (Strait et al., 2012)

Various treatments have been described for strongylidae infections in non-human primates, namely (Strait et al., 2012):

• Thiabendazole: 25 mg/kg PO q12h during 2 days; 50 mg/kg PO q24h during 2 days; 100 mg/kg PO once;
• Levamisole: 10 mg/kg SC or PO once;
• Mebendazole: 40 mg/kg PO q8h during 4 to 5 days.