Streptococcus equi ssp. zooepidemicus in camelids (Proceedings)

S. equi ssp. zooepidemicus is a Lancefield group C streptococci which causes acute, subacute, and chronic disease in camelids. It is considered to be a commensal organism of alpacas in South America, but not in North America. It is the etiologic agent of "alpaca fever" in Peru, where it reportedly causes serositis of the thoracic and abdominal cavities and is associated with a high mortality. This organism may also be carried in clinically normal horses in the nasopharynx.

Peritonitis and pleuritis are common clinical manifestations of S. equi ssp. zooepidemicus bacteremia in South American camelids. Camelids appear to have lesions restricted to the serosal surfaces, with minimal or no parenchymal lesions. It is hypothesized that stressors, including transport, may result in subclinical carriers developing systemic infection.

In Peru, estimated morbidity is 5-10%. One case report of natural infection in Canada exists of a llama which died of peritonitis. S. equi ssp. zooepidemicus has also been reported as the etiologic agent of a case of mastitis in a llama and septic orchitis in an alpaca.

The authors have seen S. equi ssp. zooepidemicus occur as a herd outbreak in Kansas and have also documented additional lesions of meningitis and endocarditis in affected alpacas. Meningitis and meningoencephalitis caused by this bacterium have been reported in humans and veterinary species, including horses and a goat. In humans, infection is most commonly associated with consumption of unpasteurized dairy products or contact with horses. Bacterial endocarditis is reported in humans with this agent,. For these reasons, S. equi ssp. zooepidemicus in camelids should be considered to have zoonotic potential.

Mortality reports from Peru range from 50-100%. The single reported case of fulminant infection in Canada died within 3 days after the cessation and subsequent reinstatement of antimicrobial therapy. In one trial of experimental infection in llamas, 6 test animals were inoculated with S. equi ssp. zooepidemicus. All animals, including controls, were euthanized and at necropsy, 4 of 6 test animals had gross evidence of polyserositis. The remaining 2 test animals with no lesions also had negative tissue bacteriologic cultures throughout the study.

The single natural infection case reported in Canada was a 7-month-old male llama, while the experimental animals ranged in age from 10-19 months. Animals in the Kansas outbreak ranged in age from 1-6 years, with four of them aged 3 years or less. From this, it would appear that young animals are predisposed to the systemic manifestation of the syndrome, although it should not be ruled out in mature animals.

Suspicion of S. equi ssp. zooepidemicus should occur when there is acute death in llamas and alpacas, where no clinical signs of illness existed prior to death. Necropsy of animals with acute death should include observation for excess fluid in the thoracic or abdominal cavities and examination of the meninges. Samples of fluids and tissues should be obtained as aseptically as possible and submitted for cytology, aerobic culture and histopathology. Depending on the clinical manifestations, animals presenting alive may have labored breathing, cyanosis, abdominal distention or colic, or severe neurologic signs. CBC and serum chemistry typically indicate severe inflammatory processes, with left shifts, hyperfibrinogenemia, hyperglycemia (common in ill camelids), and protein derangements, depending on the progression of the disease. Hyperglobulinemia and hypoalbuminemia with either a normal or elevated total protein may be seen. Thoracic and abdominal ultrasonography and cerebrospinal fluid analysis have proven useful. Definitive diagnosis is based on positive culture of cavity effusions, cerebrospinal fluid and/or blood and antimicrobial sensitivity should be performed.

Treatments which have been utilized in managing S. equi ssp. zooepidemicus polyserositis include intravenous fluid therapy, ceftiofur sodium (5 mg/kg, IV, q 12h), ampicillin sodium (12mg/kg IV, q 12h) flunixin (1 mg/kg, IV, q 12h), butorphanol (0.1 mg/kg SC) and other indicated supportive care.

It is not currently known if horses may serve as a source of this bacterium to camelids or if camelids may serve as sublinical carriers. Until more is known about the epidemiology of S. equi ssp. zooepidemicus in camelid herds, limiting species mixing, quarantine of new animals and fomite disinfection are strongly encouraged. The authors have used ceftiofur crystalline free acid (6.6 mg/kg, SC, neck) and feed-based chlortetracycline (2.2 mg/kg/day/animal) in an attempt to slow or stop an outbreak. Because the epidemiology of this bacterium in camelids is not known, the mass treatment of herds with antimicrobials is empirical and the risks associated with mass antimicrobial administration must be weighed against the risk of outbreak.

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