ECHINOCOCCUS MULTILOCULARIS COPROANTIGEN DETECTION BY ENZYME-LINKED IMMUNOSORBENT ASSAY IN FOX, DOG, AND CAT POPULATIONS * Guest scientist from Division of Veterinary and Biomedical Sciences

  • Deplazes P
  • Alther P
  • Tanner I
 et al. 
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Abstract

A sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of Echinococcus multilocularis coproan-tigens (EM-ELISA) was developed with polyclonal rabbit (solid phase) and chicken egg (catching) antibodies that were directed against E. multilocularis coproantigens and somatic worm antigens, respectively. In experimentally infected dogs and cats, coproantigens were first detectable 6-17 days postinfection (PI) in samples of 8 dogs (worm burdens at necropsy: 6,330-43,200) and from 11 days PI onward in samples of 5 cats infected with 20-6,833 worms. After anthelmintic treatment of 4 dogs and 5 cats at day 20 PI, coproantigen excretion disappeared within 3-5 days. The sensitivity of the ELISA was 83.6% in 55 foxes infected with 4-60,000 E. multilocularis, but reached 93.3% in the 45 foxes harboring more than 20 worms. The EM-ELISA was used in surveys of "normal" dog and cat populations in Switzerland. Among 660 dogs and 263 cats, 5 dogs and 2 cats exhibited a positive reaction. In 2 of these dogs (0.30%) and 1 cat (0.38%), intestinal E. multilocularis infections were confirmed by necropsy, polymerase chain reaction PCR, or both. The specificities of the ELISA in these groups were found to be 99.5% and 99.6%, respectively, if positive ELISA results that could not be confirmed by other methods were classified as "false positive" reactions. Echinococcus multilocularis, a tapeworm inhabiting the small intestine of carnivorous mammals, is the causative agent of alveolar echinococcosis, one of the most lethal helminthic infections of humans. The parasite is endemic in a large belt of the northern hemisphere stretching from North America through northern Europe, Russia, and southern Asia to China and Japan (Rausch, 1995; Schantz et al., 1995; Eckert, 1998). The sylvatic cycle of E. multilocularis predominantly involves foxes (genera Vulpes and Alopex) as definitive hosts and many species of rodents as intermediate hosts (Schantz et al., 1995). Domestic dogs and cats can also act as definitive hosts, but foxes are thought to be the main sources of environmental contamination with eggs of E. multilocularis in most of the endemic areas (Schantz et al., 1995; Eckert and Deplazes, 1997). An accurate determination of the prevalence of E. multilo-cularis in populations of final hosts is an essential requirement for establishing epidemiological baseline data and for estimat-ing the potential infection risk for humans (Eckert, 1998). Cur-rently, the most reliable technique for the diagnosis of E. mul-tilocularis infection in foxes and other definitive hosts is par-asitological examination of the small intestine at necropsy. Until recently, methods for an accurate and sensitive identification or exclusion of the infection in living animals were not available. The standard purgation technique with arecoline hydrobromide routinely used for screening dog populations for Echinosoccus granulosus is not applicable to foxes and cats. In dogs, this technique is hampered by its relatively low sensitivity (65.2% after 1 dose, 78.3% after 2 doses), and it is inefficient in up to 32% of the dogs that do not purge (Schantz, 1997). Moreover, the technique is biohazardous, labor intensive, and costly. Recent developments in serum antibody, fecal antigen, and DNA detection for the diagnosis of intestinal infections with E. granulosus or E. multilocularis have provided alternatives to current techniques (reviewed by Craig et al., 1996; Deplazes and Eckert, 1996). In particular, the detection of parasite co-proantigens by sandwich enzyme-linked immunsorbent assay (ELISA) has become a general focus of interest in the diagnosis

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Authors

  • Peter Deplazes

  • Peter Alther

  • Isabelle Tanner

  • R C Andrew Thompson

  • Johannes Eckert

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