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CHRONIC FLUORIDE POISONING (FLUROSIS)
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Fluorosis is chronic fluorine intoxication and often observed after prolonged ingestion of small but toxic amounts of fluorine in the diet/feed or fodder contaminated by industrial pollution from aluminium smelting factories, steel works, cement factories, brick kilns, coal burning electric power stations, glass manufacturing and phosphate processing units etc .
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Consumption of contaminated water or use of fluoride containing minerals or phosphate rocks as feed supplements for animals may also be responsible for fluorosis.
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Though it is a non-fatal syndrome, but productivity of the affected animals goes down.
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Animals normally ingest low levels of fluorine throughout the life as fluoride is a normal constituent of forages, especially legumes.
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The fluorine gets deposited in bones and teeth without any apparent signs of toxicity.
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There is very long latent period probably due to gradual saturation of bones and teeth with fluorine as these tissues act as sink for fluorine.
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Out of a total body load of fluorine, 95-96% is deposited in bones and teeth.
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Once these structures get saturated, fluorine ions start exerting general toxic effects. Unabsorbed fluoride is eliminated through faeces.
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Ingestion of fluoride in fodder (ppm of dry weight) at levels less than 30ppm in young cattle and milking cows, 40ppm in beef cattle, 50ppm in sheep, 70ppm in pigs, 90ppm in horses and 150ppm in chickens do not produce clinical signs of poisoning.
Sources of poisoning
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Feeds, fodder, water, mineral supplements rich in fluorine and top dressing of pastures with phosphate lime stone are the common sources of poisoning.
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These conditions have been reported from the areas adjoining industrial units emitting fluorine containing gases or dusts or the areas in the vicinity of volcanos.
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Animals ingesting vegetation/crops or grazing on the pastures where industrial effluents or the smoke and gases coming out of industrial units or volcanos settle are also poisoned.
Clinical signs
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The earliest and mildest sign is mottling, consists of light yellow, green, brown or black spots or bands arranged horizontally across the teeth.
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Occasionally, vertical bands are also seen where pigment is deposited along the enamel fissures.
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Mottling generally occurs on incisors, however, molars and premolars are worst affected which are difficult to examine. Such teeth give dull, opaque white and chalky appearance.
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If animals continue to consume fluoride containing feeds or water, mottled areas become pits, teeth become brittle and break unevenly and sometimes are reduced to the level of gums or even there is shedding of teeth in works affected cases.
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In young animals, eruption of permanent incisors is delayed, there are oblique eruptions or hypoplasia of teeth with wide gaps between the teeth.
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Due to uneven surface or shedding of teeth, mastication becomes difficult and even impossible in worst affected cases, thus there is poor growth in young and growing animals and acetonaemia in adults.
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Affected animal like to drink cold water to avoid pain while ingesting fodder.
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Other general signs are anorexia, dry and rough hair coat, ruffled fur or feathers, emaciation and reduced milk production.
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