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Bertiella Infection

[Bertiella mucronata] [Bertiella studeri]

Causal Agents

Members of the genus Bertiella are cestodes (tapeworms) of non-human primates in nature. Human infections are uncommon . B. studeri and B. mucronata have been identified in children with some contact or association with non-human primates; a few cases may have been related to contaminated fruits. There has been some suggestion that B. studeri is a species complex based on reported morphological variance among human cases.

Life Cycle

Although the life cycles of Bertiella species are not completely understood, it is generally believed the genus undergoes a two-host life cycle, with an arthropod intermediate host (usually a mite) and a vertebrate definitive host (usually non-human primates for the species implicated in human infection). Eggs and proglottids are passed in the feces of the definitive host image . Oncospheres are ingested by the arthropod intermediate host image .  In the arthropod intermediate host, the oncospheres develop into cysticercoids image . The definitive hosts become infected after ingesting arthropod intermediate hosts image infected with cysticercoids. The cysticercoid everts an unarmed scolex image , which it uses to attach to the small intestinal wall. Adults remain in the small intestine of the host image . Although rare, humans may also serve as incidental definitive hosts for Bertiella spp., usually after accidentally ingesting infected mites image .

Hosts

Bertiella studeri usually infects monkeys in the genera Anthropopithecus, Cercopithecus, Cynomologus and Macaca; B. mucronata has been recovered from monkeys in the genera Callicebus and Alouatta. Apes such as chimpanzees (Pan spp.) may also be infected, often in captive settings. Intermediate hosts are believed to be one or several species of orobatid mites.

Geographic Distribution

Bertiella mucronata is a New World species known to occur in South America and Cuba; B. studeri is an Old World species found in Africa and Asia. Imported cases have been recorded in non-endemic areas. Most human cases of bertiellosis occur in persons who have had contact with primates.

Clinical Presentation

With so few human cases reported, clinical aspects of this infection are not well defined. Many of the reported cases have been asymptomatic; however, some patients have reported gastrointestinal symptoms.

Eggs of Bertiella spp.

 

Eggs of B. studeri are spherical and measure approximately 35-51 micrometers in diameter. Eggs of B. mucronata are smaller than those of B. studeri. Eggs of Bertiella spp. have a characteristic pyriform apparatus, an inner chitinous membrane that has a pair of filamentous projections around a six-hooked embryo.
Figure A: Eggs of Bertiella sp. liberated from proglottids. The proglottids were shed from a human patient who had lived for a number of years in Africa. In several of these eggs, the pyriform apparatus can be easily seen. Images courtesy of Clinipath Pathology, Perth, Australia.
Figure B: Eggs of Bertiella sp. liberated from proglottids. The proglottids were shed from a human patient who had lived for a number of years in Africa. In several of these eggs, the pyriform apparatus can be easily seen. Images courtesy of Clinipath Pathology, Perth, Australia.
Figure C: An egg of Bertiella sp. liberated from a gravid proglottid. The arrows point to the hooklets.
Figure D: An egg of Bertiella sp. liberated from a gravid proglottid. The arrows point to the hooklets.
Figure E: Eggs of Bertiella sp. liberated from gravid proglottids. Image courtesy of the National Public Health Surveillance Laboratory, Vilnius, Lithuania.
Figure F: Eggs of Bertiella sp. liberated from gravid proglottids. Image courtesy of the National Public Health Surveillance Laboratory, Vilnius, Lithuania.
Proglottids and scoleces of Bertiella spp.

 

Adults of Bertiella studeri are 10-30 cm long and 6-10 mm thick; adults of B. mucronata can be longer to 40 cm long. The scolex of both species has a rudimentary unarmed rostellum and four oval suckers. Mature proglottids are similar in the two species but can be separated based on the structure of the vagina.
Figure A: Scolex of Bertiella studeri. Image courtesy of Richard Bradbury.
Figure C: Partially-cleared proglottids of Bertiella sp. In this image, many eggs can be seen through the proglottids. Image courtesy of the National Public Health Surveillance Laboratory, Vilnius, Lithuania.
Figure B: Proglottids of Bertiella sp.

Laboratory Diagnosis

Diagnosis is made by the finding of proglottids or, less commonly, eggs in stool. The eggs are characteristic and can be liberated from gravid proglottids.

Laboratory Safety

Standard laboratory precautions for the processing of stool samples apply. Eggs of Bertiella spp. are not infectious to humans.

Suggested Reading

Sun, X., Fang, Q., Chen, X.Z., Hu, S.F., Xia, H. and Wang, X.M., 2006. Bertiella studeri infection, China. Emerging Infectious Diseases, 12(1), p.176.

Bhagwant, S., 2004. Human Bertiella studeri (family Anoplocephalidae) infection of probable Southeast Asian origin in Mauritian children and an adult. The American journal of tropical medicine and hygiene, 70 (2), pp.225–228.

DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.