Transmission
Gnathostomiasis is transmitted by the ingestion of raw or insufficiently cooked definitive hosts such as fresh water fish, poultry, or frogs.In Thailand and Vietnam, the most common cause appears to be consumption of undercooked Asian swamp eels (Monopterus albus, also called Fluta alba) which transmit G. spinigerum. Monopterus albus is an invasive species in North America, but no Gnathostoma infections in humans have yet been conclusively identified in the US. Hosts
Intermediate host
The primary intermediate host is the minute crustaceans of the genus Cyclops. These crustaceans are then ingested by a second intermediate host, such as frogs. Definitive host
The definitive hosts for gnathostomiasis include cats, dogs, tigers, leopards, lions, mink, opossums, raccoons, poultry, frogs, freshwater fish, snakes or birds. Incubation period
The incubation period for gnathostomiasis is 3–4 weeks when the larvae begin to migrate through the subcutaneous tissue of the body. Morphology
The adult parasite is reddish-brown in color and has a globular cephalic dome that is separated from the rest of the body by constriction. The posterior portion of the nematode is smooth while the anterior half is covered with fine leaf-like spines. The head is round and contains 4 to 8 transverse rows of hooklets that are protected by a pair of fleshy lips . The males are shorter than the females, 11–25 mm (0.43–0.98 in) compared to 25–54 mm (0.98–2.13 in) respectively. Eggs are oval and have a mucoid plug at one end.
The paranoia and hallucinations can combine in the form of “threatening or accusatory voices coming from neighbouring houses [and] are frequently reported by the patients as disturbing and undeserved". Patients also present with a lack of symptoms commonly found in other mental disorders similar to paraphrenia. There is no significant deterioration of intellect, personality, or habits and patients often remain clean and mostly self-sufficient. Patients also remain oriented well in time and space.Paraphrenia is different from schizophrenia because, while both disorders result in delusions and hallucinations, individuals with schizophrenia exhibit changes and deterioration of personality whereas individuals with paraphrenia maintain a well-preserved personality and affective response. Causes
Neurological
Paraphrenia is often associated with a physical change in the brain, such as a tumor, stroke, ventricular enlargement, or neurodegenerative process. Research that reviewed the relationship between organic brain lesions and the development of delusions suggested that "brain lesions which lead to subcortical dysfunction could produce delusions when elaborated by an intact cortex". Predisposing factors
Many patients who present with paraphrenia have significant auditory or visual loss, are socially isolated with a lack of social contact, do not have a permanent home, are unmarried and without children, and have maladaptive personality traits. While these factors do not cause paraphrenia, they do make individuals more likely to develop the disorder later in life.