Outbreaks of tetanus in beef cattle and sheep in Brazil associated with disophenol injection

Outbreaks of tetanus. in which 297 beef cattle and 50 sheep were affected and died, were associated with the injection of a Clostridium tetani-contaminated anthelmintic (disophenol). The disease was observed on five farms in Rio Grande Sul, Brazil. Tetanus is an acute, often fatal, infectious disease of all species of domestic animals caused by the neurotoxin of Clostridium tetani. The condition usually develops after contamination of deep, penetrating wounds by the organism. Anaerobic conditions that may develop in such damaged tissues allow the organism to proliferate and produce a toxin, which causes the rigidity and muscle spasms characteristic of the disease (Timoney et al., 1988; Odendaal and Kriek ' 1994; Radostits et al., 1994). Although mainly considered an individual and sporadic condition, outbreaks of tetanus have often been reported in cattle (Ramsay, 1973; Crossman, 1989; Chapleo, 1991; Gray et al., 1991; Whitaker, 1991; Preece and Bostelmann, 1996; Whitehead and Ellicott, 1996; Thompson, 1997: Benavides et al., 2000) and sheep (Aslani et al., 1996). This communication describes an important outbreak of tetanus associated with a C. tetani-contaminated anthelmintic (AH) injection. Outbreaks of tetanus, in which 297 beef cattle and 50 sheep were affected and died, were observed between June and September 2001 on five farms in Rio Grande Sul, Brazil. Most cattle were 6-8 months old post-weaning Hereford or Hereford cross calves, which were kept in pastured paddocks. The calves from farms I and 2 (Table 1) were supplemented with concentrates and mineral mix. The clinical signs started Received for publication August 9, 2006 between 12 and 18 days after these animals were subcutaneously injected with a commercial AH drug (disophenol, Brazil). The distribution of animals treated with AH and deaths caused by tetanus in each farm is shown in Table 1. Stiffness, rigidity of the neck and limbs, bloat, pricked ears and prolapse of the third eyelid were initial signs. Subsequently, there was teeth grinding, hypersensitivity, tachycardia, hyperthermia, recumbency with extension of the limbs, convulsions, opistotonus and death (Fig. 1). The clinical course was 34 days. The necropsy was performed on 20 calves, in which focal large (20-30 cm diameter) oedema in subcutaneous (SC) tissues of the cervical or scapular regions were the significant lesions. Small (0.5-2 cm diameter) necrotic foci extending into muscular tissues were seen in the sites of the AH injection in eight calves. A treatment with benzathine penicillin [30 000 UI/kg intramuscular (IM), 2/2 days] and acetyl promazine (0.1 mg/kg IM, twice daily, 2 days) was attempted in 65 affected calves, but it was unsuccessful. Tetanus antitoxin was available in amount sufficient to treat (200 000 UI/animal IM) only nine animals, which survived I or 2 days more than those not treated with antitoxin. A preventive treatment with benzyl penicillin (20 000 UI/kg IM) was attempted in 410 calves (farm 2), which had been injected with the same AH 6 days later than animals on farm 1, but it did not protect 51 calves (Table 1) from tetanus. The toxicological examinations in samples of livers, kidneys, ruminal and abomasal contents, concentrates and mineral mix resulted negative for strychnine, coumarin, sodium monofluoroacetate, organophosphate and carbamates.