Lead poisoning is still the commonest poisoning of cattle reported by NADIS vets, although evidence from NADIS and the veterinary laboratories suggest that it is becoming less common (or, at least, reported less frequently). The peak time of the year for lead poisoning is turnout. Of UK farm livestock, cattle appear to be the most vulnerable to lead poisoning, with calves being the most likely victims. However, lead poisoning can occur in all domestic animals including horses, poultry and dogs. Pigs appear to be the least susceptible farmed species.
The main source of lead in most cases is rubbish. Discarded sump oil, dumped lead batteries, unwanted putty and old paint tins are amongst the commonest sources. In many cases cattle will actively eat these products as they are attracted to the oil or to the taste. Calves often ingest lead while they are playing with discarded rubbish. Drinking water from lead pipes is often suggested as a possible source of lead poisoning, but cattle do not appear to be susceptible to poisoning by this route.
As the total number of cases of lead poisoning have decreased from over 100 in 1994 to less than 50 in 2001, it has become apparent that there is a significant number of lead poisonings in grazing animals where high concentrations of lead in the soil have been implicated. These outbreaks have mostly been seen in areas where lead has been mined. Feed contamination is also a potential problem, indeed contaminated rice bran from Burma was the primary source of the last major outbreak of lead poisoning in the UK in 1989.
The signs of lead poisoning depend very much on the species involved. The description here refers only to cattle Lead poisoning can be divided into three forms: Acute, where the signs develop rapidly, chronic where the signs develop over a long period, and subacute, which has a time-scale between the first two. The type of disease seen is primarily dependent on the amount of lead eaten, the more that fs eaten the faster the signs develop. (The source of the lead can also affect the signs, but this effect is more complex). Because of their susceptibility to lead poisoning, cattle very rarely develop chronic poisoning
Acute diseaseÂ .
Â·Â Constipation followed by diarrhoea
Not all cases will show all the signs. In some cases the only presenting will be blindness or other nervous signs. It is thus important to get any animal showing strange blindness or other nervous signs checked by your vet, as they could be lead poisoning.
On clinical signs noted above you can be suspicious of lead poisoning, particularly if a source of lead can be identified. However the signs of many other nervous diseases, including listeriosis, grass staggers and vitamin A deficiency are all similar to lead poisoning, so a veterinary examination can be very valuable. This is especially important for adult cattle as BSE cases can show many of the same vague nervous signs. Also, even if the signs are suggestive of lead poisoning, further testing is necessary to confirm lead poisoning, as there may be food safety implications:
Treatment of acute cases is not worthwhile. The disease has usually progressed too far to be treated once signs are seen. Treatment has to begin early if an animal is to be saved. Treatment is complicated, costly and long. It is also NOT effective at eliminating lead faster from affected animals, so cannot be used to make cattle fit for human consumption more quickly.
In the vast majority of cases lead poisoning can be avoided by good waste management on the farm. Prevention is easier, cheaper and more effective than treatment by a vet. The most important areas for prevention are: