Screening for Echinococcus granulosus in dogs: Comparison between arecoline purgation, coproELISA and coproPCR with necropsy in pre-patent infections.

Echinococcus granulosus is an important zoonotic infection of dogs. The purpose of the present study assessed the performance of two laboratory diagnostic methods with arecoline purgation and necropsy in infected dogs. In total 65 dogs were successfully experimentally infected with protoscoleces of E. granulosus from ovine infection. At 14-34 days post-infection groups of dogs were purged with arecoline hydrobromide and then necropsied. Faecal samples were tested at weekly intervals by coproantigen ELISA and coproPCR. The necropsy infection rate with E. granulosus was 89.2 per cent. Only 43 per cent of dogs were successfully purged after one arecoline dose; this percentage increased to 76.9% for two doses of arecoline purgation. E. granulosus coproantigen was detected by coproELISA in 82.8% of faeces. The positive and negative predictive values for coproantigen ELISA were 96 and 44.4% respectively. E. granulosus DNA was detected in pre-patent faecal samples by coproPCR in 25.9% of dogs. These results indicate that coproELISA is more sensitive than arecoline purgation for the detection of pre-patent E. granulosus infection in dogs. CoproPCR detected E. granulosus DNA in dog faeces by 21 days post-infection before egg production.

Evaluation of three PCR assays for the identification of the sheep strain (genotype 1) of Echinococcus granulosus in canid feces and parasite tissues.

The performance of 3 PCR assays for the identification of the G1 sheep genotype of Echinococcus granulosus was evaluated using tissue and canid fecal samples. The "Dinkel" and "Stefanic" primers were the most sensitive in detecting E. granulosus DNA in feces of necropsied dogs (73.7% and 100%, respectively). The "Abbasi" primers detected 52.6% of E. granulosus infected dogs but were the most species-specific, cross-reacting only with Echinococcus shiquicus (tissue 90.9%; feces 75%). The Stefanic primers were the least specific (tissue, 27.3%; feces, 25%) for E. granulosus. The Dinkel primers also showed inter-species cross-reactivity (tissue, 63.6%; feces, 100%) but were found to be strain-specific for the E. granulosus G1 sheep genotype. Improvement of PCR tests for Echinococcus species and subspecific variants should rely on the use of less-conserved genes and development of protocols that improve the quality and quantity of DNA extracted from feces.