Amphimerus pseudofelineus (Ward, 1901) Barker, 1911
ETYMOLOGY:Amphi = on both sides and merus = part (referring to the break in the vitellaria) along with pseudo = false and felineus = cat host; differentiating it from Opisthorchis felineus which had already been described from cats in Europe.
SYNONYMS: Opisthorchis guyaquilensis Rodriguez et al., 1949
HISTORY: This trematode was originally described from a cat in Nebraska, USA. Barker (1911) differentiated the genus Amphimerus from that of Opisthorchis, and he transferred the species pseudofelineus to the new genus.
GEOGRAPHIC DISTRIBUTION: The Americas; besides the original description from Nebraska, Amphimerus pseudofelineus has been described from cats from Illinois, Michigan, and experimentally from Manitoba, Canada. Human infections with Opisthorchis guyaquilensis in Ecuador were later identified as Amphimerus psuedofelineus. Miyazaki (1991) states that about 10 species have been found in the america, and that all may potentially infect human. In a similar fashion, it may be that all are capable of occurring in cats.
LOCATION IN HOST: Gall bladder and bile ducts; occasionally in the small intestine.
PARASITE IDENTIFICATION:Amphimerus pseudofelineus adults are very similar to those of Opisthorchis. The major difference is that the vitelline glands situated along the side of the body are divided on each side into anterior and posterior clusters at the level of the ovary. Also, the vitellaria extend more posteriad within the lateral field.
The adults measure about 16 to 24 mm in length. The eggs are similar to those of other opisthorchids measuring 27 by 15 µm.
LIFE CYCLE: The life cycle has been incompletely described (Evans, 1963). A cat was fed 700 grams of fresh-water fish fillets from suckers, Catostomus commersonii, collected from lake Manitoba. The examination of the cat 51 days after the last feeding revealed the Amphimerus pseudofelineus within the bile ducts.
CLINICAL PRESENTATION AND PATHOGENESIS: Infection of cats can result in severe cirrhosis of the liver ultimately resulting in death (Levine et al., 1956; Rothenbacher and Lindquist, 1963). In chronic cases the liver can be enlarged with a granular appearing surface. Cut sections of the liver appear fibrotic with a distinct yellow-brown mottling. The larger bile ducts may contain a dark-brown exudate. Bile duct epithelium becomes thickened and fibrotic. Clinical signs reflect progression in liver dsyfunction with anorexia, weight loss, diarrhea, periodic vomiting, and icterus, with hepatomegally initially, then microhepatica.
TREATMENT: Praziquantel is likely to prove successful in eliminating these trematodes.
EPIZOOTIOLOGY: Cats are not the only hosts of this parasite. It has also been reported from coyotes in the USA and as Opisthorchis guayaquilensis in dogs in Ecuador and in cats and opossums, Didelphis marsupialis in Panama. A related species, Amphimerus lancea, has been reported from fresh-water porpoises in Brazilian waters.
HAZARD TO OTHER ANIMALS: None known.
HAZARD TO HUMANS: There have been records of human infections with this parasite in Ecuador where 4% of the human beings and 3% of the dogs in a village were found to be infected (Rodriguez et al., 1949). It is believed that the infections were obtained by the ingestion of raw fish.
CONTROL/PREVENTION: Prevent the ingestion of infected lizards, toads, and frogs.
Barker FD. 1911. The trematode genus Opisthorchis R. Blanchard, 1895. Studies Zool Lab Univ Nebraska 103:513-561.
Evans WS. 1963. Amphimeruspseudofelineus (Ward, 1901) (Digenea: Opisthorchidae) and its second intermediate host in manitoba. Can J Zool 41:649-651.
Levine ND, Beamer PD, Maksic D. 1956. Hepatitis due to Amphimeruspseudofelineus in a cat. J Parasitol 42(suppl):37.
Rodriguez JD, Gomez LF, and Montalvan CJA. 1949. El Opisthorchisguayaquilensis (una nueva especie de Opisthorchis encontrada en el Ecuador). Rev Ecua Hig Med Trop. 6:11-24.
Rothenbacher H, Lindquist WD. 1963. Liver cirrhosis and pancreatitis in a cat infected with Amphimeruspseudofelineus. JAVMA 143:1099-1105.
Miyazaki I. 1991. Helminthic Zoonoses. 494 pages. International Medical Foundation of Japan. Fukuoka, Japan.
Figure 2-37. Amphimeruspseudofelineus recovered from the bile duct of a cat in Temple, Texas, USA, by Dr. DM Bandy.