Botulism in Cattle Associated with Osteophagy in the State of Acre, Brazil

Abstract

Background:Botulism is a non-febrile intoxication resulting from the ingestion of Clostridium botulinum neurotoxins manifested by partial or complete flaccid paralysis of the musculature of locomotion, swallowing and respiration. The objective of this study was to report the first case of botulinum intoxication associated with osteopathy in the state of Acre, as well as to alert breeders and veterinarians to the incidence of this disease in cattle farming.

Case: The present report is an outbreak of botulism in the municipality of Acrelândia, in the state of Acre, which resulted in the death of 16 Nelore beef cattle in approximately 30 days. The affected animals were females in reproductive phase maintained under extensive breeding system. The main clinical signs presented were weakness in the pelvic limbs, prostration, recumbency and death in less than 48 hours. Only one animal, with similar symptomatology, was found alive and submitted to emergency therapeutic measures, but without success. During the necropsy of this bovine, no significant changes were found, only related to the decubitus and agony time, except for fragments of long bones visualized in the reticulum. Samples of bone particles, ruminal contents, reticulum, rumen and intestine fragments were collected for the detection of botulinum toxins by the mouse bioassay method, as well as brain and brain stem for differential diagnosis of rabies and bovine spongiform encephalopathy by direct immunofluorescence and immunohistochemistry, respectively. The samples were sent to the Laboratory of General Bacteriology of the Biological Institute, São Paulo, Brazil, and all the analyzes presented negative results.

Discussion: One of the main risk factors for the occurrence of botulinum toxin is the presence of carcasses in the pastures, added to the deficiency of phosphorus and other minerals. The cattle develop the habit of gnawing bones and tissues from dead animals in the field. With this exercise, animals can ingest pre-formed toxins in corpses, as decomposing remains offer an anaerobic environment conducive to spore development and toxin production. Bovine females, in breeding, present greater nutritional need than adult males and younger animals. This is because the reproductive phase increases the demands of minerals, vitamins and organic compounds that participate in the female's reproductive physiological process. In this case, the inadequate supply of minerals may stimulate the osteopagic practice of cadaveric remains in the pastures, making the bovids susceptible to botulism. Diagnosis is established by means of clinical signs, epidemiological characteristics and absence of specific anatomopathological findings. Confirmation is given by the isolation of the toxin in the body of the diseased animal. However, the lack of detection of this does not rule out the possibility of occurrence of the disease, in view of the rapid passage of the neurotoxin through the hematogenous route and through the tissues before reaching the neuromuscular junctions. In suspect cases, it is important to perform a differential diagnosis for other diseases that demonstrate clinical symptoms of neurological or acute neuromuscular character. The description of this outbreak, besides exposing the first notification of botulism in the state of Acre, shows the epidemiological relationship between the main risk factors and the occurrence of the disease in the Brazilian herds.