The excretion of Salmonella typhimurium in the faeces of calves fed milk substitute

Abstract

SUMMARYA total of 495 calves in 16 batches were examined (117 calves in 4 batches in 1979 and 378 in 12 batches in 1982). They were purchased in markets, transported by road to a farm in Somerset and reared on a milk substitute diet for a period of up to five weeks. Salmonella typhimurium phage type DT 193 was endemic in 1979 and phage type DT 204c in 1982. The mortality rates in the two years were 9S4 % and 1-9% respectively. The causes of death were not investigated although the majority were probably due to salmonellosis.The rate of isolation of S. typhimurium from the rectal faeces of calves in all groups was either zero or relatively low on arrival. It rose to a peak (which was higher in 1979) in the second or third weeks before declining to low levels by the end of the fourth week of residence on the farm.Data from 162 calves, examined twice weekly for four weeks in 1982, indicated that the distribution of infected calves, based on the number of times that S. typhimurium was isolated from each, was not random. The calves could be assigned to two main categories; those from which the organism was never isolated and those from which it was isolated at least twice. This suggested that salmonella infected calves actively excreted the organism.The association between salmonella excretion and medication of sick animals with antibacterial drugs was strongest during the second week. Over the four-week period nearly 40 % of the calves found to be excreting S. typhimurium were not treated, indicating a high incidence of subelinical infection.Salmonella excretion by the calves followed a regular pattern and infection was self-limiting within five weeks. The peak in the salmonella excretion rate and the mortality rate were higher in 1979 when phage type DT 193 was the endemic strain. However, in 1982 the calves received 100 p.p.m. furazolidone in their milk ration during the first week of their stay on the farm, and this may have contributed to the differences noted between the two years.

The epidemiology of salmonella infection of calves: the role of dealers

“…Indeed on one of the premises (Fig. 1) the salmonella isolation rates increased after cleaning and disinfection and it has been suggested that the use of pressure hoses may cause aerosols and spread salmonellas to other parts of the building [11]. It is also possible that vigorous cleansing and disinfection may have washed salmonellas out from previously untouched areas.…”

Further observations on the excretion of salmonella in the faeces of calves fed milk substitute

“…It is probable that these animals contracted infection either on their farm of origin, or in the market or markets through which they passed, or from the lorry or lorries in which they were transported. S. newport, a serotype which had not been isolated by us previously in this farm (Linton, Timoney & Hinton, 1981;Hinton & Linton, 1982;Hinton et al 1983 and unpublished observations) was probably contracted from one of these sources since in three of the four exeretors it was first isolated within three days of their arrival on the farm.…”

“…This investigation represents an extension of studies carried on this farm in 1979 and 1982 (Hinton et al 1983). In the event the situation in shed A was not strictly comparable with the earlier years since the incidence of salmonella infection was lower, and in one batch, a serotype other than S. typhimurium, namely S. newport, was isolated.…”

“…The methods for isolation and identification of salmonella were the same as those employed in 1982 (Hinton et al 1983).…”

“…In 1982, 162 calves in batches 7, 8, 9, 15 and 16 had been sampled twice weekly (Hinton et al 1983). In order to obtain a direct comparison with the situation in that year all the 144 calves in batches 17-20 were also sampled twice weekly.…”