Evaluation in rabbits of the fetal effects of maternal ingestion of Solanum malacoxylon

Toxic Wasting Disorders in Sheep

Simple Summary

There are several substances, either inorganic or organic that may be toxic for sheep. Intoxications by some of these substances have an acute clinical course with specific signs and lesions that may guide the diagnostic procedures. However, there are other insidious, subacute to chronic presentations, usually related to continuous intake of the toxic substance over long periods of time, that may present with emaciation, ill-thrift, and/or poor external aspect. In such scenarios, diagnosis may be challenging and should be achieved through a combination of history of exposure, subtle gross and histological findings (if present), and available ancillary tests.

Abstract

Infectious and parasitic agents have been frequently associated with debilitating and wasting conditions in sheep. The prevalence of these agents has probably undermined the role of toxic causes as contributors to such disorders. In addition, many of these intoxications frequently produce acute clinical disease with specific and characteristic lesions, thus a causal relationship with the toxic substance may be relatively easy to establish. However, persistent exposure to some of these organic or inorganic toxic substances may lead to emaciation, ill-thrift, and poor external aspect. The anti-nutritional factors and alkaloids of several plants, including pyrrolizidine alkaloids, among others, have also been associated with emaciation and/or poor general performance in sheep flocks. In this review, some of these disorders are discussed with an emphasis on clinical signs and lesions, relevant diagnostic aspects, and available therapeutic approaches. In most cases, demonstrating a history of exposure should be one of the most relevant aspects of the diagnostic approach, and removing the animals from the toxic source is the cornerstone of the majority of the treatment strategies.

Calcinosis--calcinogenic plants

The calcinogenic plants are among the most noxious plants to animals in the world. The pathological and biochemical effects of calcinogenic plants in cattle, sheep, goats, pigs, horses, buffalo and laboratory animals have been determined. The chemical nature of the toxic agents and the precise mechanism by with the calcinogenic plants induces calcinosis have been defined. Most of the active principle present as steroidal glycoside is hydrolyzed in intestine, rumen and other tissues or by the bacterial flora releasing the steroidal fragment, in most cases 1,25(OH)(2)D(3). The excess of vitamin D stimulates CaBP synthesis and calcium and phosphate absorption, producing hypercalcemia and/or hyperphosphatemia. The excessively absorbed mineral cannot be physiologically accommodated, and the deposition in soft tissues results in calcinosis. The different means of treatment of calcinosis and control of calcinogenic plants are discussed with regards to their effectiveness. A number of potential uses of calcinogenic plants have been suggested but none has been exploited on a large scale. The understanding of the mechanisms involved with calcinosis contributed enormously to the compression of vitamin D mechanism. Research methods were developed and improved but a lot is to be done in this fascinating subject.