Abstract

Introduction

Within the European Endangered Species Programme (EEP), a 6.5-year-old Przewalski horse (Equus caballus przewalskii) stallion originating from “Tierpark Sababurg” (Germany) was assigned to the Przewalski breeding group of the Royal Zoological Society of Antwerp (RZSA). The horse had been declared fit to travel by the veterinarian in charge. Before departure, the horse was immobilized, based on an estimated body weight of 250 kg, with 4.9 mg etorphine hydrochloride and 20 mg acepromazine maleate (Large Animal Immobilon, Vericore Ltd, Marlow, Bucks, UK). Simultaneously, his hooves were trimmed, blood was taken for routine analysis, an intradermal tuberculin test was performed, a transponder was inserted subcutaneously, he was vaccinated against tetanus and influenza, and a prophylactic dose of 250 mg vitamin E (DL­alpha tocopherol acetate) and 7.5 mg selenium (sodium selenite) (Etosol-Se®, Eurovet, Heusden-Zolder, Belgium) was administered intramuscularly. After 45 minutes, the animal was injected with the antidote: 6.52 mg diprenorphine hydrochloride (Revivon, Vericore Ltd, Marlow, Bucks, UK) intravenously and the same dose intramuscularly, which put him back on his feet in a few minutes. On arrival in Belgium, the animal was put in a separate stable. The next day he was dewormed with 60 mg ivermectin (Eqvalan® paste, Merial, Brussels, Belgium), and fecal analysis was carried out. Because the horse was very anxious to join the other horses in the outdoor enclosure, the introduction scheme was shortened.

Case Report

First the stallion was introduced to the most docile mare, and both supported each other well. Second, three other mares and one gelding were put together with them. Later on, many fights were observed. Especially the gelding, and to a lesser extent one of the mares, reacted very aggressively. Six days later, the gelding had to be removed from the group and was translocated to another zoo. A few more days later, the stallion had gained total control over his mares.

During the first 3 weeks, routine fecal examinations remained negative. Four weeks after arrival, an acute heavy diarrhea developed and Salmonella Virchow was isolated. The stallion was isolated and treated. Table 1 shows the evolution of the disease. This Salmonella was resistant against ceftiofur, intermediate resistant against streptomycin, but sensitive for ampicillin, amoxycillin-clavulanic acid, doxycycline, enrofloxacin, gentamycin, kanamycin and trimethoprim-sulfonamide. The stallion was injected with kanamycin-penicillin during the period of anorexia, and then treatment was continued with trimethoprim-sulphadiazine perorally. Although the animal weakened enormously in the beginning, it started to eat hay again on day 6 and survived. Subsequent fecal cultures did not reveal any Salmonella.

Table 1. Evolution of salmonellosis in a male Przewalski horse

^aElectrolytes were given daily (glucose 20 g, NaCl 3 g, NaHCO₃ 3 g, KCl 1.5 g/L drinking water)
^bKanacillin Trifortis, Continental Pharma, Brussels, Belgium
^cFinadyne®, Schering-Plough, Brussels, Belgium
^dEmdotrim 60% Mix, Ecuphar, Zuienkerke, Belgium

Four days after the end of the acute illness, the horse started limping on the left hind leg. Flunixin (Finadyne®, Schering-Plough, Brussels, Belgium) 1.1 mg/kg was administered perorally for 3 days, and limping decreased gradually during 5 days but reappeared thereafter. Then, 1 g phenylbutazone was given orally daily, and 10 days later a small bleeding was observed at the coronary region. Thereafter, no more limping was observed.

Three weeks later, the horse suddenly had lost its left hind-leg hoof with only minimal bleeding. The animal was put in a stable with a rubber floor with disinfectant. The first day, the stallion was biting in its foot, but administering flunixin stopped this behavior. For the next 10 weeks, 1 g phenylbutazone was given daily perorally combined with vitamins and minerals containing biotin (Equitop® Forte, Boehringer Ingelheim, Brussels, Belgium). Additionally, trimethoprim-sulphadiazine was given for 2 weeks. Unexpectedly, the stallion started to use its leg again after 9 days, and 3 months later the hoof had grown halfway. Five and a half months after exungulation, a full new hoof was formed, and the animal was released in the outdoor enclosure with the mares.

Discussion and Conclusion

Salmonellosis is a very well-known disease in livestock, but reports on Salmonella Virchow in equines are very scarce.⁵ Severe dysentery is a hallmark in equine salmonellosis and can occur when animals are exposed to stress.³ The stallion was most probably a carrier that became ill during a very stressful period, although a new infection cannot be ruled out, as fecal contamination by birds is a risk factor.² Albeit that, none of the other horses got sick. Treatment of salmonellosis is a standard procedure involving regular administration of electrolytes.³ In wild animals, however, this remains difficult, because they are unapproachable. Anyhow, the oral administration of electrolytes is safer than the intravenous one with regard to a possible hyperkalemia.³ Laminitis can be a result of severe diarrhea and bacterial toxin and has been observed in Przewalski horses before.^1,3,4 One of the reasons for exungulation is terminal laminitis.³ Only anecdotal reports (personal communications) of exungulation in exotic species exist. There is no standard treatment for sloughing of the hooves,³ but all measures taken in this case contributed to a positive outcome.

Literature Cited

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2.  Mörner, T. 2001. Salmonellosis. In: Williams, E.S. and I.K. Barker (eds.) Infectious Diseases of Wild Mammals, 3rd ed. Iowa State University Press, USA. Pp. 505–507.

3.  Radostits, O.M., D.C. Blood and C.C. Clay (eds.). 1994. Veterinary Medicine—A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses. 8th ed. Bailliere Tindall, London, England. Pp. 515, 730–747, 1617–1621.

4.  Stewart, M.C., J.L. Hodgson, H. Kim, D.R. Hutchins and D.R. Hodgson. 1995. Acute febrile diarrhoea in horses: 86 cases (1986–1991). Austr. Vet. J. 72: 41–44.

5.  Van Duijkeren, E., M.M. Sloet van Oldruitenborgh-Oosterbaan, D.J. Houwers, W.J. van Leeuwen and H.C. Kalsbeek. 1994. Equine salmonellosis in a Dutch veterinary teaching hospital. Vet. Rec. 135: 248–250.