Page 93 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

60 SECTION | I General

VetBooks.ir sulfur, As, and tellurium (Khanal et al., 2010). It acts as a nitrate poisoning were diagnosed in a dairy herd due to
consumption of green grass, mainly alfalfa, which was irri-
bio accumulator which means plants and animals retain
gated with a municipally treated wastewater. Five cows
the element in greater concentrations than are present in
the environment and the element can be bioconcentrated were found dead and seven fetuses were aborted.
by 200 6000 times (Gupta, 1988; Dhillon and Dhillon, Methemoglobin was increased while hemoglobin was
1991a,b). The disease is more common in southern parts decreased. A clinical picture included difficulty in breath-
of Asia, in times of drought or where less irrigation water ing, shivering, and brown discoloration of the mucous
is predisposed to high soil Se levels and a greater uptake membranes of the vulva, vagina, and conjunctiva. The
of Se by plants (Ghosh et al., 1993; Kunli et al., 2004; postmortem findings included dark brown carcasses,
Yadav et al., 2005; Tiwary et al., 2006). The disease is nonclotted blood in the dilated vessels. Cardiac hemor-
commonly known as Se toxicosis. The poisoning is more rhages, pulmonary, and rumen congestion; edema and
common in forage-eating animals such as cattle, sheep, hyperemia of the mucous membranes of the abomasums
horses, and other herbivores that may graze Se-containing and small intestine were noticed in all examined animals.
plants (Dhillon and Dhillon, 1991a,b). In acute toxicosis, The postmortem examination of aborted fetuses revealed
the blood and serum Se concentrations were .3 4 ppm, severe ascites and hydrothorax. Affected animals
and in chronic toxicosis .1 2 ppm. Chronic selenosis responded well to the treatment with methylene blue
was often reported in winter season with the symptoms of (Al-Qudah et al., 2009). In another incidence of poisoning
hair loss, cracks on skin, hooves and horns, leading to at Kopargaon (Maharashtra), India, fourteen crossbred
elongation and sloughing of hooves, lameness, ataxia, and animals died within 1 day and the source was detected to
recumbency (Gupta et al., 1982). In an experimental study be fodder of Bajari. All available fodders in eight farms
with buffalo calves, adverse effects appeared when the were tested and were found to be positive for nitrate/
whole blood Se concentrations increased above 2 μg/mL, nitrites (Rawte, 2012).
with mortality occurring when blood levels exceeded Nitrate/nitrite poisoning in buffalo, cattle, goat and
3.4 μg/mL (Deore et al., 2002; Deore et al., 2005). sheep has also been reported from several other southern
The disease is commonly known as alkali disease in parts of Asia (Shinozaki, 1975; Sidhu et al., 2008; Al-
cattle and horses and exhibit weight loss, hair loss (espe- Qudah et al., 2009; Sidhu et al., 2011). Although poison-
cially obvious in the mane and tail), and lameness in all ing in monogastric animals is rare, in India, in one form a
four limbs (Gupta, 1988). The coronary bands are painful number of poisoning cases have been reported in pigs,
to palpation and the bands may separate with excretion of wherein several of them died within very short period.
necrotic tissue from the defect. In severe cases the hoof Young pigs are more at risk of nitrate/nitrite induced tox-
wall sloughed off. The other form of disease is known as icity because they have microflora that can convert nitrates
“blind staggers” (commonly observed in cattle and sheep), into nitrites. This might be the reason for the sudden death
animals developed a staggery gait, wandered aimlessly, of eight young piglets within 12 h of feed intake and 12
and “head pressed.” Other symptoms included nausea, severely affected young ones that died despite treatment
vomiting, nail discoloration, brittleness, hair loss, fatigue, (Mahajan et al., 2007; Sidhu et al., 2014; Susan, 2016). In
irritability, and foul breath odor (often described as “garlic another incidence one rare outbreak of nitrate poisoning in
breath”) (Dhillon and Dhillon, 1991a,b; Ghimire, 2012). combination with classical swine fever in a small pig farm
has also been reported (Sidhu et al., 2014). These findings
do indicate nitrate poisoning in pigs is more common in
Nitrate and Nitrite
India than other countries of the world (Vyt, 2006;
Nitrate can accumulate in many crop and pasture plants, Rathnapraba et al., 2012).
weeds, and forages such as berseem (Trifolium alexandri-
num), bajra (Pennisetum glaucum), maize (Zea mays), oats Fluorosis
(Avena sativa), sorghum (Sorghum vulgare), and toriya
(Brassica napus). Many species are susceptible to nitrate Chronic exposure to fluoride in groundwater causes
and nitrite poisoning, but there is considerable difference adverse health problems not only in humans, but also in
in susceptibility. Ruminants are much more susceptible to various species of domestic animals in the form of fluoro-
nitrate poisoning than monogastric animals (Gupta, 2016). sis. The primary manifestations are mottling of teeth
In India, there are several documented cases of nitrate (dental fluorosis) and andosteosclerosis of the skeleton
poisoning in cattle but it is rare in horses. The disease is (skeletal fluorosis). Besides these maladies, nonskeletal
also very common in other parts of Asia. Most cases fluorosis or toxic effects of chronic fluoride exposure in
involve ingestion of nitrate/nitrite-contaminated water, soft tissues, such as gastrointestinal discomforts, neuro-
nitrate fertilizer directly, or forage or hay grown in the area logical disorders, impaired endocrine and reproductive
of a previous fertilizer spill. In one incidence 23 cases of functions, teratogenic effects, apoptosis, genotoxic effects,