Vibriosis causes serious economic loss in beef herds through reproduction wastage. An investigation conducted from 1992-94 showed that 46% of cases of infertility in cattle in NSW was caused by vibriosis (Hum, 2007). Vibriosis, caused by the bacteria Campylobacter fetus subspecies venerealis, typically causes early embryonic death with return to oestrus. Abortion rates are usually low - up to 5% but maybe as high as 20% (Radostits et al, 1994). This usually occurs between 4-7 months. The bull is the carrier transmitting the infection to the cow at service.
In September 2014, I was called to a property in the West Wyalong area. 16 homebred heifers were joined to one bull at the beginning of October 2013 for 10 weeks. They weighed approximately 400kg. 44 cows were added to the herd 2 weeks later for an 8 week joining. The bull had been owned for 2 years and was approximately 5 years old. He was a replacement bull for a previous bull purchased from the same stud in 2008. This bull was replaced because he did not appear to produce a great number of calves.
The herd had previously been run with a continuous joining. In 2013 the producer decided to change to a set joining period and start pregnancy testing.
Cows with calves at foot had been introduced to the herd 18 months earlier.
The cattle had been grazing natural pastures and supplemented with wheaten hay for most of the year. There were mice in the hay shed. The spring, summer and autumn had been ‘tough’ with a late break in June 2013 resulting in improved pastures conditions. No pigs had been seen in the area. There were no cattle on neighbouring properties. The herd had been on agistment for 1 month between joining and scanning.
Heifers and cows were scanned at the end of February (10 weeks after the bull came out).
When samples were collected the heifers were all in body condition score 4/5 and appeared healthy.
|Heifer No||BVDV Antibody||L. hardjo||L. pomona||Campylobacter IgA Antibody|
This is an unusual presentation for bovine vibriosis as the disease typically causes early embryonic loss with abortion occurring less frequently. Following colonisation of the uterus, the bacteria causes a tissue reaction in the uterus. Fertilisation occurs followed usually by early embryonic death. If death of the embryo occurs before maternal recognition of the pregnancy the cow returns to oestrus 3 weeks later. If early embryonic death occurs after this point then the cow will return to oestrus at irregular intervals - typically 30 day later (Arthur et al, 1983.). With continued service by the infected bull infection continues until the cow gradually develops immunity. At this point the uterine reaction is reduced and early embryonic death does not occur. In some of these animals quite extensive disease of the foetal membranes can develop which is likely to result in abortion at around 4-7 months. (Arthur et al, 1983). Laboratory results appear to support the likelihood that this has happened in the majority of heifers who had conceived successfully with abortion the result. Leptospirosis and pestivirus been ruled out as possible causes of abortion.
The cows appear to have been less severely affected by vibriosis presumably having developed some immunity from the previous practice of continual joining and running with the infected bull. Lower than expected conception rates in the herd could also be due to a high cow to bull ratio and a tough spring at joining time.
This case highlights the need to consider vibriosis when investigating abortion in cattle.