Listeriosis in Sheep

A comparison was made between a hay fed group, consisting of 23 ewes, and a grass silage fed group of 22 ewes, all pregnant. Excretion of Listeria monocytogenes (Lm) in the faeces and milk, antibody titres in sera and whey and delayed hypersensitivity against Lm, and several blood components were determined. The animals had previously been exposed to Lm, and Lm was isolated from the faeces from several animals when the experiment started. No significant difference in number of excretors between the 2 groups was found during the experimental period. The haemagglutination titres in both sera and whey were low and on the same level in both groups. The titres were higher in animals with 1 foetus than in animals with more than 1 foetus. In the first part of the experimental period the silage group had a reduced number of lymphocytes, lower total serum protein values and higher serum iron values, compared with the hay group. The silage group also had a stronger delayed hypersensitivity reaction against Lm than the hay group, and in the silage group the reaction was significantly stronger in ewes with 3 or more foetuses than in ewes with 1 foetus. In conclusion, the combined effect of some of the changes found in animals fed grass silage may leave them more susceptible to infections.     

Listeriosis in Sheep

Two hundred and ninety-one grass silage samples from 113 farms with recent outbreaks of listeriosis were examined for the presence of Listeria monocytogenes (Lm). The frequency of Lm isolations increased with increasing pH. Lm was isolated from 22 % of the samples with pH < 4, from 37 % with pH 4–5 and from 56 % with pH > 5. Formic acid had been used as additive. A similar investigation was carried out on 32 samples from a farm with no outbreak of listeriosis during the investigation period. Lm was isolated from 9 samples.     

Listeric Septicaemia in Sheep Associated with Tick-Borne Fever (Ehrlichiosis Ovis)

Sheep is apparently fairly resistant against infections with Listeria monocytogenes (Lm). Grønstøl (unpublished) found that a high proportion of healthy sheep are carriers of Lm. In such animals Lm may cause clinical disease when resistance is lowered. Tick-borne fever (TBF) is known to reduce the resistance against several infections (Øverås 1972). This report describes listeric septicaemia associated with TBF.     

Listeria Monocytogenes Excretion and Humoral Immunity in Goats in a Herd with Outbreaks of Listeriosis and in a Healthy Herd

In a herd of 65 goats with outbreaks of listeriosis (Herd A) blood, faeces and milk were collected just after the outbreaks, about 1 month later and at delivery about 4 months thereafter. Faeces and milk were examined bacteriologically and blood and milk serologically for Listeria monocytogenes (Lm), and the results were compared with those of 2 similar samplings in a healthy herd (Herd B). In Herd A Lm was isolated from faeces in 5 of 14 septicaemic does and in 6 of 48 other animals on the first sampling, and in 4 and 1 animals respectively, on the subsequent 2 samplings. In milk Lm was demonstrated just after the outbreaks only, viz. in 3 of 12 septicaemic does and in 16 of the other 32 examined. Four does excreted Lm in both faeces and milk on this date. In Herd B Lm was demonstrated only at delivery, i.e. from 10 of 43 animals. Most of the isolates belonged to serotype 1. Reciprocal geometrical mean titres (GMT) of antibodies in sera from the septicaemic group decreased from 236 to 140 and 136 respectively on the subsequent samplings, whereas GMT of the encephalitic animals and of the remainder of Herd A increased from about 20 to about 100 at delivery. GMT of Herd B increased toward delivery from 23 to 39, with largest increase for the does. GMT in whey were ≤ 18 for all groups.     

Clinical Investigations in a Goat Herd with Outbreaks of Listeriosis

The majority of 50 nonpregnant dairy goats in a herd showed acute symptoms of disease for 1–2 days after a sudden change in weather conditions, feeding regime and management. In 17 of the does the condition progressed with symptoms of septicaemia with depression, fever, inappetence and hypogalactia for a period of up to 5 weeks. Only 1 of these 17 animals died. Three weeks after the first symptoms were seen, 7 other animals showed typical symptoms of listeric encephalitis. All but 1 recovered within 2 weeks. Treatment with penicillin seemed to have good effect against both these disease forms. The does with symptoms of septicaemia had significantly higher antibody titres against Listeria monocytogenes than the animals with encephalitis and the remainder.     

Listeriosis in Sheep

Listeriosis in sheep. Listeria monocytogenes excretion and immunological state in healthy sheep. Acta vet. scand. 1979, 20, 168–179. — The excretion of Listeria monocytogenes (Lm) in the faeces and milk, and humoral and cell mediated immunity against Lm, were examined in a sheep flock where no cases of listeriosis had occurred during the last 3 years. The investigation was carried out during the indoor season. During the first part of the season 2 of the 10 pregnant, 8 months old lambs excreted Lm in the faeces, but none of the 106 ewes, 2–10 years old. At lambing the organism was isolated from the faeces of 6 of the 10 1 year old lambs and from 64% of the ewes, and from the milk of 1 of the lambs and 41% of the ewes. Nearly all the isolates (98.5%) belonged to serotype 1. Antibody titres against Lm were found in sera and whey by an indirect haemagglutination method. The titres were higher for the ewes than for the hoggs and seemed to be influenced by the number of foetuses the animals carried. Cell mediated immunity was determined by a skin test where delayed hypersensitivity against an antigen prepared from Lm, was measured. Animals fed grass silage had a stronger reaction than animals fed hay, and a stronger reaction was found in animals with ≥ 3 foetuses than in the remainder. The investigation indicates that even in a healthy sheep flock all the animals may be exposed to Lm, and the majority may be latent carriers and excrete this organism in the faeces and milk during periods of stress.