Page 372 - Small Animal Internal Medicine, 6th Edition

344 PART II Respiratory System Disorders

FUNGAL PNEUMONIA kellicotti in dogs and cats, Aelurostrongylus abstrusus in cats,
and Crenosoma vulpis in dogs.
VetBooks.ir Common mycotic diseases that can involve the lungs are often within intermediate or paratenic hosts, that subse-
Infection occurs as a result of ingestion of infective forms,
blastomycosis, histoplasmosis, and coccidioidomycosis. In
most cases, organisms enter the body through the respira-
response often occurs within the lungs, causing clinical signs
tory tract. The infection may be successfully eliminated quently migrate to the lungs. An eosinophilic inflammatory
without the animal showing clinical signs, or the animal may in some, but not all, infected animals. The definitive diagno-
show only transient respiratory signs. The infection may also sis is made by identification of the characteristic eggs or
progress to cause disease involving the lungs alone or may larvae in respiratory or fecal specimens (see Chapter 20).
spread systemically to various target organs. Cryptococcal
organisms also enter the body through the respiratory tract CAPILLARIA (EUCOLEUS) AEROPHILA
and can infect the lungs, particularly in cats. However, the Capillaria aerophila, also known as Eucoleus aerophila, is a
presenting signs in cats are generally those of nasal infection. small nematode. Adult worms are located primarily beneath
Pulmonary signs are most often the primary presenting the epithelial surfaces of the large airways. Clinical signs
complaint in dogs with blastomycosis and in cats with develop in very few animals with Capillaria infection, and
histoplasmosis. the disease is most often identified through the fortuitous
Pulmonary mycoses are considered in the differential identification of characteristic eggs during routine fecal
diagnoses of dogs or cats with progressive signs of lower examination.
respiratory tract disease, especially if they occur in conjunc- The rare animal that displays signs shows signs of allergic
tion with weight loss, fever, lymphadenopathy, chorioretini- bronchitis. Thoracic radiographic findings are generally
tis, or other evidence of multisystemic involvement. Thoracic normal, although a bronchial or bronchointerstitial pattern
radiographs typically show a diffuse, nodular, interstitial may be seen. Tracheal wash fluid can show eosinophilic
pattern of the lungs (see Fig. 20.6). The nodules are often inflammation. Capillaria is diagnosed by the finding of char-
miliary. The presence of this pattern in dogs with suspi- acteristic eggs in tracheal wash fluid or fecal flotation mate-
cious clinical signs supports a diagnosis of mycotic infec- rial (see Fig. 20.12, C).
tion, although similar radiographic patterns can be seen The treatment of choice for dogs and cats is fenbendazole
with neoplasia; parasitic lung disease; infection with atypical (50 mg/kg PO q24h for 14 days). Levamisole (8 mg/kg PO
bacteria such as Mycobacterium, Actinomyces or Nocardia; for 10-20 days) has also been used successfully in dogs. Iver-
and eosinophilic lung disease. Other potential radiographic mectin has been suggested for treatment, but a consistently
abnormalities include alveolar and bronchointerstitial effective dosage has not been established. The prognosis in
patterns and consolidated regions of lung. Hilar lymph- animals with the disease is excellent.
adenopathy can occur, most commonly in animals with his-
toplasmosis. The lesions caused by histoplasmosis can also PARAGONIMUS KELLICOTTI
be calcified. Paragonimus kellicotti is a small fluke. Both snails and cray-
Organisms can be retrieved by tracheal wash in some fish are necessary intermediate hosts, thus limiting the
cases. However, because of the interstitial nature of these disease to animals that have been in the region of the Great
diseases, bronchoalveolar lavage or lung aspiration may Lakes, in the Midwest, or in the southern United States. Pairs
be necessary (see Figs. 20.15 and 20.16). Fungal culture is of adults are walled off by fibrous tissue, usually in the caudal
probably more sensitive than cytologic analysis alone. An lung lobes, with connection to an airway to allow for the
inability to find organisms in pulmonary specimens does passage of eggs. A local granulomatous reaction may occur
not rule out the diagnosis of mycotic disease, however. A around the adults, or a generalized inflammatory response
complete discussion of systemic mycoses is provided in to the eggs may be noted.
Chapter 97. Infection is more common in cats than in dogs. Some
dogs and cats have no clinical signs. When clinical signs are
present, they may be the same as those seen in animals with
PULMONARY PARASITES allergic bronchitis. Alternatively, signs of spontaneous pneu-
mothorax can result from the rupture of cysts.
Several parasites can cause lung disease. Certain intestinal The classic radiographic abnormality is single or multiple
parasites, especially Toxocara canis, can cause transient solid or cavitary mass lesions, most commonly present in the
pneumonia in young animals, usually those younger than a right caudal lobe (see Fig. 20.10). Other abnormal patterns
few months of age, as the larvae migrate through the lungs. seen on thoracic radiographs can be bronchial, interstitial
Infection with Dirofilaria immitis can result in severe pulmo- (reticular or nodular), or alveolar in nature, depending on
nary disease through inflammation and thrombosis (see the severity of the inflammatory response (see Fig. 20.11).
Chapter 10). Oslerus osleri resides at the carina and main- Infection is diagnosed definitively through identification
stem bronchi of dogs and is discussed in Chapter 21. The of the ova in fecal specimens (using the sedimentation tech-
other primary lung parasites that are most commonly diag- nique described in Chapter 20), tracheal wash fluid, or bron-
nosed are Capillaria (Eucoleus) aerophila and Paragonimus choalveolar lavage fluid (see Fig. 20.12, D). Multiple fecal