Bertiella cestodes (tapeworms) normally parasitize non-human primates, but under some circumstances they can infect humans. Most reported cases have involved B. studeri or B. mucronata and have been in children who have had some contact with non-human primates.
The life cycle of Bertiella species is not completely understood. Bertiella are believed to have two-host life cycles, with an arthropod intermediate host (usually a mite, likely an oribatid mite) and a vertebrate definitive host (usually non-human primates for the species implicated in human infections). Bertiella studeri (which is found in Africa and Asia) usually infects monkeys in the genera Anthropithecus, Cercopithecus, Cynomologus, and Macaca.
Bertiella eggs and proglottids (the repeated hermaphroditic reproductive segments of tapeworms) are passed in the feces of the definitive host. Oncospheres (which contain the tapeworm larvae) are ingested by the arthropod intermediate host and within this host the oncospheres develop into cysticercoid larvae. The definitive hosts become infected when they ingest arthropod intermediate hosts infected with cysticercoids. Adult Bertiella reside in the small intestine of the definitive host, where they attach to the mucosa with the aid of an unarmed scolex (the anterior end of a tapeworm's head). Humans can occasionally serve as definitive hosts, usually after accidentally ingesting infected mites.
Human infections with B. studeri have been reported from Borneo, India, Java, Malaysia, Mauritius, Singapore, the Philippines, Sri Lanka, Thailand, and Yemen.