A review on hemato-biochemical, accumulation and patho-morphological responses of arsenic toxicity in ruminants

Abstract

Arsenic is an environmental pollutant that has received significant attention in recent years due to its adverse effects in animals. It is a contaminant of concern because it is found in both water and fodder due to natural and anthropogenic sources (e.g. pesticide use coal burning industry). Over the past decade, arsenic levels have been increasing in the water in certain regions of Pakistan. The excess amount of arsenic in water and fodder results in the accumulation of the metalloid in animal tissues, including livestock that inhabit these regions. The objective of this article is to review current data on arsenic accumulation, as well as arsenic-induced hematobiochemical and histopathological changes, in small and large ruminants in order to synthesize the current state of the science. In ruminants, reports on the toxic effects of arsenic have included reductions in body weight and changes in hematocrit parameters. Arsenic exposure has led to major abnormalities in the blood and tissues of animals prior to the excretion in the urine and feces. The analysis of hematologic and biochemical parameters following arsenic exposure has revealed that arsenic alters the homeostasis of these endpoints in livestock due to poisoning. Increased activities of liver enzymes, for example aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in arsenic-exposed animals are indicative of liver damage. The absorbed arsenic is metabolized in the liver and eliminated in the bile and urine through the process of biomethylation. Histopathological studies of liver in ruminants have revealed that chronic oral exposure to arsenic causes severe damage to the liver. Moreover, the kidneys of arsenic-exposed animals show profuse hemorrhaging in the medulla, and indications of glomerular damage. Acute tubular necrosis indicated by pyknotic nuclei in proximal convoluted tubules is also observed with arsenic toxicity. The epithelial cells around the renal blood vessels can become necrotized, as indicated by the presence of fibrosis tissue that replaces the damaged areas. Arsenic accumulation and subsequent damage in animal tissues, as well as its excretion in the environment through urine and feces, is a concern for both animal and human health. This is especially true for human consumption of contaminated meat or milk from livestock which can result in exposure to high levels of arsenic exposure. This review is anticipated to act as an important source of information for the current status of arsenic toxicity in ruminants.

Keywords:

• Arsenic
• drinking water
• livestock
• fodder
• urine

Disclosure statement

The authors have no conflict for the publication of this review article.