Page 113 - Problem-Based Feline Medicine

7 – THE COUGHING CAT 105

bolism, or acute pulmonary inflammation and edema ● Lung changes vary from patchy pulmonary infil-
associated with worm death. Acute respiratory distress trates to severe alveolar densities suggestive of
syndrome (ARDS) and generalized respiratory failure lung lobe atelectasis or consolidating pneumonia.
are not uncommon. Occasionally pleural effusion is present.
Acute death is reported in approximately 30–45% of Cardiac ultrasound may show hollow linear densi-
cats presenting with clinical signs of heartworm disease. ties (worms) in the right chambers and pulmonary
artery, as well as pulmonary arterial dilation.
Vomiting is often reported and when it occurs together
● Cardiac ultrasound has similir sensitivity to anti-
with respiratory signs, it is suggestive of chronic feline
gen tests. False negatives occur because worms
heartworm disease.
may reside in the extremities of the pulmonary
A gallop rhythm is sometimes audible. arteries where they cannot be detected with the
ultrasound. Occasionally, false-positive results
Neurological signs such as blindness and vestibular
may occur from linear densities detected where
signs may be associated with aberrant migration of L4
the main pulmonary artery branches.
larvae to the brain.
A report describes two cases of cutaneous nodular
lesions associated with D. immitis adult parasites in Differential diagnosis
domestic short-haired cats living in an endemic area
in northern Italy. Other causes of chronic coughing or acute respiratory
distress should be considered as differentials.
● Lungworm and lung flukes are diagnosed with
fecal Baermann exams.
Diagnosis ● Feline asthma is not associated with vomiting, and
Mild non-regenerative anemia, peripheral basophilia, basophilia is uncommon.
eosinophilia and hyperglobulinemia are sometimes ● Cardiomyopathy is diagnosed with echocardiog-
evident. raphy.
● Hydrothorax is diagnosed radiographically and
Heartworm testing. classified based on examination of the fluid.
● Antigen tests (ELISA test) are highly specific, but ● Other forms of pneumonia, (bacterial, viral,
only moderately sensitive. False negatives occur fungal, inflammatory), and neoplastic disease
with low numbers (< 5) worms, and as most cats may appear similar, and are differentiated by lack
have only one or two worms, the test is positive in of evidence of feline heartworm on serology,
less than 50% of infected cats. radiology and ultrasound. Radiography, serology
● Antibody tests are more sensitive, but less specific and cytological or histological examination of tis-
for active infection than antigen testing, as they sue may provide a definitive diagnosis.
may remain positive for 18 months after infection
has resolved.
● A higher sensitivity and specificity is obtained if
Treatment
both the antigen and antibody tests are performed
and the results considered together. Asymptomatic cats do not require treatment and
● Microfilarial tests are unreliable in the cat spontaneous resolution of infection may occur as
because the concentration of microfilaria is very worms live only about 1.5–2 years in cats.
low and microfilaremia is transient, lasting only
Symptomatic cats.
1–2 months.
● Stabilize with oxygen therapy, prednisone (1–2
Thoracic radiographs may show dilated and blunted mg/kg PO q 12–24 h for 10–14 days, then slowly
pulmonary arteries, which are most prominent in the wean down), bronchodilator therapy (Theophylline,
caudal pulmonary arteries, particularly the right side. The TheoDur® 25 mg/kg PO q 24 h) and if needed
dilation may not be evident beyond the cardiac shadow. antiemetics.