''Cyrtosomum penneri'' are roundworms of the family

Atractidae Atractidae is a family of nematodes belonging to the order Rhabditida Rhabditida is an order of free-living, parasitic and microbivorous nematodes living in soil. The Cephalobidae, Panagrolaimidae, Steinernematidae, and Strongyloididae ...

that are found in the intestines or lungs of various vertebrate animals. They do not produce eggs; instead the adults produce larvae that are ready to infect as soon as they leave their mother's womb. ''C. penneri'' is found only in

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

Transmission

Unlike most nematodes, which infect their host by being accidentally swallowed, ''C. penneri'' is acquired through sexual transmission. In lizards, it is passed through the

cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

of the infected lizard to the cloaca of the other during mating, and it has been found, through experiments, that female contraction is 100% percent, while male contraction is about 70%. In an experiment by the Department of Biology at

Florida Southern College Florida Southern College (Florida Southern, Southern or FSC) is a private college in Lakeland, Florida. In 2019, the student population at FSC consisted of 3,073 students along with 130 full-time faculty members. It offers undergraduate, gradua ...

, the researchers found that land snails and crickets do not serve as transport or

intermediate host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include ...

s, which supports the idea that ''C. penneri'' is transferred only during sexual intercourse of the definitive host.

References

Rhabditida Sexually transmitted diseases and infections Nematodes described in 1957 {{parasitic animal-stub