HAMMONDIA HEYDORNI: EVIDENCE OF GENETIC DIVERITY AMONG ISOLATES FROM DOGS.

Authors: SREEKUMAR, C - USDA,ARS,ANRI,APDI; Hill, Dolores; Miska, Kate; Rosenthal, Benjamin; VIANNA, M C - USDA,ARS,ANRI; VENTURINI, L - LA PLATA, ARGENTINA; BASSO, W - LA PLATA, ARGENTINA; GENNAN, S - SAO PAULO, BRAZIL; LINDSAY, D - BLACKSBURG, VA; Dubey, Jitender

Submitted to: Experimental Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2004
Publication Date: 5/1/2004
Citation: Sreekumar, C., Hill, D.E., Miska, K.B., Rosenthal, B.M., Vianna, M.B., Venturini, L., Basso, W., Gennan, S.M., Lindsay, D.S., Dubey, J.P. 2004. Hammondia heydorni: evidence of genetic diverity among isolates from dogs. Experimental Parasitology. 107:65-71.

Interpretive Summary: Hammondia heydorni is a single-celled parasite of livestock. Dogs are its main reservoir hosts. Scientists at the Beltsville Agricultural Research Center report genetic biodiversity among 14 isolates of H. heydorni and compare results with closely related parasites. The results will be of interest to biologists, parasitologists and veterinarians.

Technical Abstract: Isolates of Hammondia heydorni from dogs form Argentina, Brazil and the United States were analysed for genetic diversity. A total of 14 isolates were tested for their ability to produce amplification using three PCR assays, one targeting the common toxoplasmatiid ITS-1 region and 2 amplifying novel, H. heydorni- specific loci, HhAP7 and HhAP10. While the ITS-1 fragments could be amplified from all isolates, only 6 isolates were capable of amplifying the specific target fragments from the novel loci. The resulting PCR products were further investigated for genetic diversity using restriction fragment length polymorphism (RFLP) and single strand conformation polymorphism (SSCP) techniques. RFLP polymorphism was evident only at the HhAP10 locus, differentiating 2 Argentinean isolates from the rest. Mobility shifts on SSCP gels revealed that the 2 Argentinean isolates were not only different from the other 4 isolates, but were also different from each other both at HhAP7 and HhAP10 loci. The ITS-1 fragments of all isolates were identical by RFLP. However, 2 distinct mobility patterns were noticed on SSCP gels. Sequence analysis of the three PCR fragments confirmed the SSCP findings. Based on the sequence data, from the ITS-1 and the 2 random loci, the isolates could be broadly classified into 2 distinct groups, with minor differences/polymorphisms evident within these groups. In contrast, very little heterogeneity was noticed in the sequences of corresponding ITS-1 regions of Neospora caninum and Toxoplasma gondii isolates, available in the public database. The present study reveals that there is a considerable degree of microheterogeneity among isolates of H. heydorni. This diversity should be taken into consideration while comparing the