Dirofilaria
immitis is a pathogenic heartworm responsible for feline heartworm disease. To
study this heartworm, scientists rely on shelter animal autopsies. Though this
heartworm is seen in both cats and dogs, it is much more prevalent in dogs. In Yabsley et al.’s experiment they studied
shelter dogs and cats in northwestern South Carolina to determine the threat of
heartworm infection for dog and cats living in that area (Yabsley et al., 2004).
It was discovered that the dogs infected with D. immittis were also infected with D. reconditum which is a nonpathogenic filarial worm. According to
Chalifoux and Hunt’s study, a noteable difference between the two are that D. immitis shows enzyme activity in
excretory and anal pores whereas D. reconditum shows uniform enzyme activity (Chalifoux,
Hunt, 1971).
Though they are oftentimes found
together, the two parasites are quite different. D. reconditum finds a definitive host in dogs through the
intermediate host Ctenocephalides felis
(a flea) and Heterodoxus spiniger
(lice) (Nolan, University of Pennyslvania).
D. immitis is more versatile,
finding dogs, foxes, wolves, coyotes, and cats all good definitive hosts and
lives in the right chamber of the heart as well as pulmonary arteries of its
host (Ferris, 1999). Aside from their hosts and enzymatic activity,
morphologically D. immitis and D. reconditum differ in head shape, tail
shape, and body movement. Though their differences do not seem large, as we
have all learned in entry level biology, shape can absolutely determine
function. I would venture to assume that the seemingly subtle differences
between these two parasites may be why one is pathogenic and one is not.
Works Cited
Chalifoux, Laura, and Ronald
Hunt. "Histochemical Differentiation of Dirofilaria Immitis and
Dipetalonema Reconditum." Journal of the American Veterinary Medical
Association 158.5 (1971): 601-05. Print.
Ferris, Howard.
"Dirofilaria Immitis." Nemaplex. University of California,
n.d. Web. 11. Oct. 2012
Nolan, Tom and Kim Mah.
"Dipetalonema Reconditum Homepage." Diagnosis of Veterinary
Endoparasitic Infections. University of Pennsylvania, 2004. Web. 11 Oct.
2012.
Yabsley, M. J., C. Dresden-Osborne, E. A.
Pirkle, J. M. Kirven, and G. P. Noblet. "Filarial
Worm Infections in Shelter Dogs and Cats from Northwestern South Carolina,
U.S.A." Comparative Parasitology 71.2 (2004): 154-57. Print.
The abundance of strays in the country does not help the situation by fueling the lifecycle of parasites such as heartworm. Aside from that, I knew that cats are not as prone to heartworm, but it is interesting that they typically have one species of heartworm, while being more common in dogs, dogs have two species.
ReplyDeleteI had no idea Dipetalonema got this far north. Creepy. Did the paper say what the overall prevalence was?
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