Page 288 - Small Animal Internal Medicine, 6th Edition

260 PART II Respiratory System Disorders

administered initially for 1 week. If a beneficial response is highly suggestive of aspergillosis are sensitivity to palpation
seen, the drug is continued for a minimum of 4 to 6 weeks. of the face or depigmentation and ulceration of the external
VetBooks.ir If signs recur after discontinuation of drug after 4 to 6 weeks, nares (see Fig. 13.2). Lung involvement is not expected.
Systemic aspergillosis in dogs is generally caused by
the same antibiotic is reinstituted for even longer periods.
If no response is seen after the initial week of treatment,
the drug should be discontinued. Another antibiotic can be Aspergillus terreus and other Aspergillus spp. rather than A.
fumigatus. It is an unusual, generally fatal disease that occurs
tried, although further evaluation for another, as yet unidenti- primarily in German Shepherd Dogs. Nasal signs are not
fied, primary disorder should be pursued. Further diagnostic reported.
evaluation is particularly warranted in dogs because, com-
pared with cats, they less frequently have idiopathic disease. Diagnosis
Frequent stopping and starting of different antibiotics every No single test result is diagnostic for infection with aspergil-
7 to 14 days is not recommended and may predispose the losis. The diagnosis is based on the cumulative findings of a
animal to the growth of resistant gram-negative infections. comprehensive evaluation of a dog with appropriate clinical
signs. As aspergillosis can be an opportunistic infection,
Prognosis underlying nasal disease must also be considered.
Bacterial rhinitis is usually responsive to antibiotic therapy. Radiographic signs of aspergillosis include well-defined
However, long-term resolution of signs depends on the iden- lucent areas within the nasal cavity and increased radiolu-
tification and correction of any underlying disease process. cency rostrally (see Fig. 14.7). Typically no destruction of the
vomer or facial bones occurs, although the bones may appear
roughened. However, destruction of these bones or the crib-
NASAL MYCOSES riform plate may occur in dogs with advanced disease.
Increased fluid opacity may be present. Fluid opacity within
CRYPTOCOCCOSIS the frontal sinus can represent a site of infection or mucus
Cryptococcus neoformans is a fungal agent that infects cats accumulation from obstructed drainage. The bones sur-
and, less commonly, dogs. It most likely enters the body rounding the frontal sinus may be thickened or appear
through the respiratory tract and, in some animals, may moth-eaten. In some patients the frontal sinus is the only site
disseminate to other organs. In cats clinical signs usually of infection.
reflect infection of the nasal cavity, central nervous system Imaging by computed tomography (CT) is preferred over
(CNS), eyes, or skin and subcutaneous tissues. In dogs signs nasal radiography. The enhanced imaging allows for more
of CNS involvement are most common. The lungs are com- accurate assessment of extent of disease. The presence or
monly infected in both species, but clinical signs of lung absence of plaques in the frontal sinuses (Fig. 15.2), integrity
involvement (e.g., cough, dyspnea) are rare. Clinical features,
diagnosis, and treatment of cryptococcosis are discussed in
Chapter 97.
ASPERGILLOSIS
Aspergillus fumigatus is a normal inhabitant of the nasal
cavity in many animals. In some dogs and, rarely, cats, it
becomes a pathogen. The mold form of the organism can
develop into visible fungal plaques that invade the nasal
mucosa (“fungal mats”) and fungal granulomas. An animal
that develops aspergillosis will rarely have another nasal con-
dition such as neoplasia, foreign body, prior trauma, or
immune deficiency that predisposes the animal to secondary
fungal infection. Most often no underlying disease is identi-
fied. Excessive exposure to Aspergillus organisms may explain
the frequent occurrence of disease in otherwise healthy
animals. Another type of fungus, Penicillium, can cause signs
similar to those of aspergillosis. FIG 15.2
Computed tomography scan of a dog with nasal
Clinical Features aspergillosis. The right side is unaffected, providing
Aspergillosis can cause chronic nasal disease in dogs of comparison for the abnormalities on the left (L). There is
any age or breed but is most common in young male dogs. lysis of the nasal turbinates with increased soft-tissue density.
Irregularly shaped soft tissue is apparent in the left frontal
Nasal infection is rare in cats. The discharge can be mucoid, sinus (*), which was confirmed to be a fungal plaque
mucopurulent with or without hemorrhage, or purely hem- during frontal sinusotomy performed for debridement and
orrhagic. The discharge can be unilateral or bilateral. Sneez- infusion of clotrimazole cream. There is also mild osteitis of
ing may be reported. Features that are not common, but are the bone surrounding the left frontal sinus.