Platynosomum fastosum

Platynosomum fastosum (syn. Platynosomum concinnum) – lizard poisoning fluke.

• Trematodes (flukes) have indirect life cycles that require one or two intermediate hosts to reach their infective stage.
• Adults are in the bile ducts of cats. Operculated eggs leave the host via feces. Terrestrial snails ingest the eggs and sporocysts containing cercariae develop in the snail. The sporocysts may leave the snail and are ingested by terrestrial isopods (pill bugs, sow bugs) or ingested by several species of amphibians or reptiles (lizards – Anolis spp., toads, geckos, skinks) where they encyst as metacercariae in the bile duct or gall bladder. A cat then ingests these hosts. The metacercariae will excyst and migrate to the bile ducts of the cat and mature.

• Adult flukes are 4-8mm long.
• Eggs are dark brown, operculated and 34-50 x 20-35µm. Eggs contain a ciliated miracidium which can usually be seen.

• Severe disease and clinical signs are often absent in cats with few worms (<125).
• Severity of disease is proportional to the number of flukes and duration of infection.
• Infected cats may experience temporary inappetence, low fever, lethargy, weight loss, poor haircoat.
• Severe clinical signs include vomiting, jaundice and diarrhea.
• Chronic infections can result in biliary hyperplasia and liver failure
• “Lizard Poisoning” refers to disease as a result to ingesting lizards containing the P. fastosum infective stage (metacercariae) and subsequent infection with the fluke – not as a result of ingesting the lizard itself.

• Platynosomum fastosum is a liver fluke of cats in Florida, other areas of the southeastern United States, and Hawaii.
• Prevalence has been reported at 15-85% in tropical and subtropical environments.
• Most common in cats that are allowed to hunt.

• This is a parasite of felidae.
• Other animals in a household are usually not at risk of obtaining infections due to the need for an intermediate host.

• Eggs are found in the feces about 4-5 weeks after reaching the bile duct of an infected cat.

• The adult worms are found in the bile ducts of cats.
• Liver and bile duct lesions include cholangitis, hepatic fibrosis, cholangiohepatitis and cholangiocarcinomas.
• Hepatomegaly has also been reported.

• Eggs can be found in feces by fecal sedimentation. Eggs are dense and rarely float.
• Multiple fecal exams may be necessary.
• Reports have suggested the use of corn oil (2ml/kg) orally to increase the number of potential fluke eggs (cat must have a patent biliary system). Repeat fecal exam within 24hrs of administration of corn oil.
• Eggs may not be seen in feces if bile ducts are occluded.

• Evans and Green (1978) reported efficacy using praziquantel at 20mg/kg. Eggs were still visible in feces 9 weeks post treatment. Treatment should be repeated at 12-week intervals.
• Foley (1994) indicated praziquantel at 10mg/kg for 3 days in mild or moderately ill cats was efficacious.
• Supportive care may also be necessary for infected cats.

• Cats should not be allowed to hunt to prevent ingestion of the intermediate hosts.

No human health hazard appears to be associated with P. fastosum.

• Andrade RLFS, Dantas AFM, Pimentel LA, Galiza GJN, Carvalho FKL, Costa VMM, Riet-Correa F. Platynosomum fastosum-induced cholangiocarcinomas in cats. Vet Par. 2012; 190:277-280.
• Foley RH. Platynosomum concinnum infection in cats. Compend Contin Educ Pract Vet.1994; 16(10):1271-1277.
• Haney DR, Christiansen JS, Toll J. Severe cholestatic liver disease secondary to liver fluke (Platynosomum concinnum) infection in three cats. J Am Anim Hosp Assoc. 2006; 42:234-237.
• Rodriguez-Vivas RI, Williams JJ, Quijano-Novelo AG, Bolio GME, Torres-Acosta JFJ. Prevalence, abundance and risk factors of liver fluke (Platynosomum concinnum) infection in cats in Mexico. Vet Rec. 2004; 154:693-694.
• Xavier FG, Morato GS, Righi DA, Maiorka PC, Spinosa HS. Cystic liver disease related to high Platynosomum fastosuminfection in a domestic cat. J Fel Med Surg.2007; 9:51-55.