980 
ANIMAL DISEASES 
I 
drug can be mixed with feed or given orally 
daily until two months after the end of the in- 
fectious season. i*''^^'^" 
Clearance of MF is at present achieved with 
the cyanine dye, dithiazine iodide, and treat- 
ment of the adult worms is with organic arseni- 
cals or organophosphates. The latter have 
proved very effective but must be used with 
great care because of the danger of other com- 
monly used cholinesterase inhibitors, such as 
those in flea collars. 
Although methods of diagnosis of infections 
with D. immitis have not improved greatly, the 
availability of inexpensive chemoprophylaxis, 
which can be readily administered where large 
groups of dogs are maintained, provides a much 
more optimistic outlook for heartworm-free 
dogs that can be used in research. 
SUMMARY 
Although D. immitis is prevalent in most of 
the United States, it is most prevalent through- 
out the southeastern region of the country. Cur- 
rently used technics for concentration of blood 
can detect essentially all infections with micro- 
filaremia, but as microfilariae are absent during 
prepatency, as well as in a small percentage of 
infected dogs, examination of blood cannot pro- 
vide diagnosis of all infections. False-positive 
reactions are common in presently-available im- 
munological tests for heartworm. Thus the 
principal utility of these tests is epidemiological, 
not diagnosis of individual cases. There has 
been little change in the treatment of estab- 
lished heartworm infections, but the prophy- 
lactic use of diethylcarbamazine provides a 
method by which colonies of dogs can be main- 
tained free of heartworm. 
REFERENCES 
1. Orihel, T. C: Morphology of the larval stages of 
Dirofilaria immitis in the dog. J. Parasitol., 47:251- 
262, 1961. 
2. Casey, H. : Pathological changes in kidneys of dogs 
infected with Dirofilaria immitis. Second University 
of Florida Symposium on Canine Heartv/orm 
Disease, 1971. 
3. Pranks, M. B. : Specific soluble antigen in the blood 
of filarial patients. J. Parasitol., 32:400-406, 1946. 
4. Beaver, P. C, Pacheco, G. and Wong, M. M.: i 
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to filariasis. Second Medical Conference on Para- i 
sitic Diseases, SEATO Medical Laboratories, 1966. 
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66-77, 1964. , 
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1971. I 
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laria immitis in hunting dogs from an area in 1 
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8. Newton, W. L. and Wright, W. H.: The occurrence i 
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Am. J. Vet. Res., 30:27-32, 1969. j 
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