Nocardial Infections of Canines and Felines

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Nocardiosis is an acute, chronic, suppurative or granulomatous infectious actinomycetic disease of humans as well as animals including dogs and cats (Walton and Libke, 1974; Pal, 1982,; Davenport and Johnson, 1986; Pal, 1988, 1997; Pal 2007; Ribeiro et al., 2008). The disease is recorded from many countries of the world (Harris, 1980; Pal, 1988; Pal, 1999; Ribeiro et al., 2008). In India, nocardial infection have been reported from the cattle, sheep, goat, buffalo, dogs, birds and humans (Pal, 1997). The first report of disease in dog was published by Trolldenier 1903 (Pal, 2007). The disease may occur in sporadic as well as endemic form.
Nocardiosis is more common in dogs than cats; and no sex, age or breed predilection has been reported. Nocardiosis in dogs and cats occur as sequel to canine distemper and feline leukemia, respectively. Disease is encountered in immunocompromised and immunocompetent hosts. Hitherto, there is no record of transmission of nocariodsis from animal to man or man to animal. It is believed that the soil serves as the source and reservoir of Nocardia infection (Pal,
1999). The disease is considered saprozoonosis, as the etiologic agent exists as saprobe in environment from where humans and animals can at least acquire the infection (Pal, 1999). The present paper describes nocardial infections in dogs and cats.
Etiology
There are at least 12 species of the genus Nocardia (Quinn et al., 2002). Of these, N. asteroides is the chief cause of nocardiosis in humans as well as animals (Haris, 1980; Pal, 1982, 1988, 1997). Less frequently, N. brasiliensis and N. otitidiscaviarum (caviae) is also implicated in the disease. Nocardia is a Gram positive, partially acid-fast, slow growing, non-motile, uncapsulated, thin, branched, filamentous, actinomycete (Pal, 2007). This acid-fast actinomycete was described for the first time by Edmond Nocard in 1888 from cattle. The actinomycetes are bacteria that lack eukaryotic nuclei and mitochondria, and have the ability to form Gram-positive branching filaments of less than 1Wm in diameter. They often produce a lesion that resembles those produced by fungi. The organism occurs as saprophyte in nature
and is recovered from the soil, decaying vegetation, dust and air. In India, N. asteroides has been isolated from the soil (Pal, 1997).

Transmission
The respiratory tract is the principal portal of entry of the organism. The source of infection is exogenous; and animals acquire the infection by inhaling a large number of infectious agents containing dust from the contaminated environment (Pal, 1999). Occasionally, the pathogen may enter the host’s body following traumatic injury/ abrasion wound on the skin by the contaminated objects (Pal, 2007). The organism may also gain entry to the body through
ingestion (Quinn et al., 2002). Occasionally, the infection may disseminate throughout the body involving organs such as spleen, kidney, brain, adrenal gland etc.

Clinical Spectrum

Dog: Nocardiosis is common in pups. The disease in canine is manifested with high fever, reduced appetite, dysponea, coughing, pneumonia, hemoptysis, nasal and ocular discharge, empyema, salivary gland abscess, abdominal swelling, depression, diarrhoea, weakness, emaciation, lymphadenitis, lameness, paralysis, incoordination and convulsion (Walton and Libke, 1974; Ackerman et al., 1982; Pal, 2007). The cutaneous or subcutaneous form of nocardiosis which simulates human mycetoma shows purulent draining sinuses producing “tomato-soup like” exudates (Pal, 2007). Superficial abscesses rupture and discharge pus that contains flakes of necrotic tissue. Unusual case of neurological disorder like rabies due to N. asteroides has been observed in dogs. The animal made an unprovoked attack on a child
resulting into extensive bite wounds on both legs. The dog died after 8 days of illness and on post-mortem examination, the brain was found positive for pathogen but proved negative for rabies virus. Vertebral osteomyelitis has also been recorded (Ribeiro et al., 2008). Rarely, N. otitidiscaviarum (caviae) is reported to cause a rapidly fatal infection in a dog (Kinch, 1968). In disseminated form, which occurs typically in young dogs less than one-year old, clinical signs are non-specific (Quinn et al., 2002). The lungs and bronchial lymphnodes contain suppurative
and grnulomatous lesions.
Cat: In feline, multiple, ulcerative, draining lesions with thick, serosanguineous exudates containing yellow granules has been noticed on the thorax and paw (Davenport and Johnson, 1986). N. brasiliensis has been reported to cause purulent lymphadenitis. In addition, peritonitis, pyothorax and involvement of lungs are observed (Pal, 2007).

Diagnosis
The diagnosis of nocardiosis is confirmed by direct detection of thin, delicate, branched, filaments of <1 Wm in diameter in the aspirates, exudates, tissues from granulomas by Gram’s method and modified cold Kinyonn acid-fast technique using 1% aqueous sulphuric acid (Pal, 1997). The organism can be easily isolated from the clinical specimens such as pus, empyema fluid, cerebrospinal fluid, biopsied and autopsied tissues, etc. on blood agar, brain heart
infusion (BHI) agar, Sabouraud dextrose agar without antibiotics. The culture plates/slants are incubated aerobically at 370C up to 10 days. Colonies become visible after incubation of 4-5 days. On blood agar, they are white, powdery, chalky and firmly adherent to the agar; colonies of N. asteroides are variably hemolytic and odourless (Quinn et al., 2001). Flat, glabrous to raised, dry wrinkled, soft or waxy whitish yellow to yellowish-orange colored colonies grow on
Sabouraud medium (Pal, 1982). Recently, the first author tried Pal’s sunflower seed medium to isolate N. asteroides from the clinical specimens of humans (Pal, 2007). Some strains of N. asteroids may grow well on Lowenstein Jensen (LJ) medium. Buffer charcoal- yeast extract (BCYE) medium which is used for isolation of Legionella can also be employed to grow Nocardia. Smears prepared from the colonies reveal some thin filaments with rod and coccal
forms by Gram method (Quinn et al., 2002). Nocardia organism can also be demonstrated in histopathological tissue sections by Brown and Brenn technique. The histopathological examination reveals clusters of nocardial filaments (Quinn et al., 2002). Immunological tests are not proved very useful in the diagnosis of nocardiosis. The pathogenicity of the organism is conducted in mice, guinea-pig and rat. Molecular techniques such as DNA probe may be
employed for the identification of individual species of Nocardia (Quinn et al., 2002). The disease should be differentiated from actinomycosis, canine distemper, neoplasm and other chronic diseases.

Treatment
Nocardia species are sensitive to antibacterial antibiotics and therefore, the dogs and cats affected with nocardial infections can be treated with ampicillin, erythromycin, minocycline, tetracycline, amikacin, oxytetracycline, gentamycin, imipenem-cilastatin, sulfadiazine, and trimethoprim-sulphamethxazole (Quinn et al., 2002; Pal, 2007). Trimetoprim-sulphadiazine causes aplastic anemia and other hypersensitive reactions in Doberman Pinschers and other dogs. Minocycline seems to be a good alternative to sulphonamide allergic patients. Cutaneous and subcutaneous lesions require surgical excision. The nodules and abscesses are excised and later 2% solution of tincture iodine, povidone-iodine solution (1:10 dilution), betadine is applied topically. The antibiotic therapy is reported to be less effective in canine nocardiosis (Quinn et al., 2002). Response to chemotherapy is poor unless treatment is started early. The
recovery rate in cutaneous form, pulmonary form and disseminated form is 80%, 50% and 10%, respectively.

Prevention and Control
Since nocardiosis is a saprozoonosis and the organism occurs in the environment, control seems to be impracticable. However, in order to minimize the prevalence and incidence of the disease, the pet animal should not be taken to the dusty environment. The dog and cat pen should be kept in sanitary conditions. The animal shed should have good ventilation and the overcrowding should be avoided. The pets receiving trauma, injury, bruise or cut to the skin
should be immediately attended. The exudates, excreta or other body discharges should be properly disposed off to prevent the spread of Nocardia organisms in the environment.

Acknowledgments
We wish to thank Dr. Ram Krishan and Dr. Govind Narayan for sending some of the relevant literature on the subject.

References
Ackerman, N; Grain, E. Jr. and Castleman, W. 1982. Canine nocardiosis. Journal of American Animal Hospital Association 18: 147-153.
Davenport, D. J. and Johnson, G. C. 1986. Cutaneous nocardiosis in cat. Journal of American Veterinary Medical Association 188: 782-729.
Kinch, D. A. 1968. A rapidly fatal infection caused by Nocardia caviae in a dog. Journal of Pathology and Bacteriology 95: 540-546.
Nocard, M. E. 1888. Note sur la maladie des boeufs de la Guareloupe connue sous le nom de farcin. Annales de li Institute Pasteur 2: 293-302.
Pal, M. 1982. Etiological significance of Nocardia asteroides in corneal ulcer of cattle. Current Science 51: 533-534.
Pal, M. 1988. Spontaneous nocardial infection in grey parrot (Psittacus erithaagus). Indian Veterinary Medical Journal 12: 252-254. Pal, M. 1997. Nocardia asteroides as a cause of pneumonia in a buffalo calf. Review of Scientific Technical Office International Des Epizootics 16: 881-884.
Pal, M. 1999. Nocardiosis: A Saprozoonosis. The Veterinarian 23: 13-14.
Pal, M. 2007. Veterinary and Medical Mycology. Directorate of Information and Publications of Agriculture, India Council of Agricultural Research, New Delhi, India.
Quinn, P. J; Markey, B. K; Carter, M. E; Donnelly, W. J. C. and Leonard, F. C. 2002. Veterinary Microbiology and Microbial Disease. Blackwell Science Ltd, Oxford, U. K.
Ribeiro M. G; Salerno T; Mattos-Guaraldi de A. L; Camello T. C. F; Langoni H; Siqueira A. K; Paes A. C ; Fernandes M. C. and Lara G. H. B. 2008. Nocardiosis: An overview and additional report of 28 cases in cattle and dogs. Revista Institute Medicine Tropical St. Paulo 50:177-185.
Stevens, D. A; Pier, A. C; Beaman, B. L; Morozumi, P. A; Lovett, I. S. and Houaang, E. T. 1981 Laboratory evaluation of an outbreak of nocardiosis in immunocompromised hosts. American Journal of Medicine 71: 928-934.
Walton, A M. and Libke, K. G. 1974. Nocardiosis in animal. Veterinary Medicine and Small Animal Clinician 69: 1105-1107.

Contributors

Mahendra Pal1, Sihin Tesfaye1 and Bulto Giro Boru2
Faculty of Veterinary Medicine. Addis Ababa University. P.O. Box No. 34, Debre Zeit, Ethiopia.

  1. Department of Microbiology, Immunology, Epidemiology and Public Health.
  2. Department of Parasitiology and Pathology.

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