Diagnostic rate in bovine abortion is oftendisappointing (see Fig. 1), but for best results thesamples to be taken are (see Caldow, 2002):l Complete foetus (or sterile samples of foetal

serum and stomach content) l Placenta (or vaginal swab)l Maternal serum (no paired samples required).

Positive results indicate exposure to disease(BVD, IBR (BHV-1), Leptospira hardjo andNeospora) or vaccine. Antibody levels remainraised for a prolonged period, so that positiveresults cannot confirm the cause of abortion,though are useful to indicate Neospora. Negativeresults confirm absence of disease

l Bulk milk samples for BVD, IBR (BHV-1) andLeptospira hardjo, provide backgroundinformation about presence of these diseases inthe herd.Again absence is the result of value.

l It should be noted that abortion caused by IBRwithout clinical signs of respiratory disease hasnot been shown to occur in UK

In this herd, diagnosis of Salmonella Dublin wasconfirmed by culture of vaginal swabs from abortedcows. The clinical signs, pyrexia, milk drop andscouring, were also strongly suggestive ofsalmonellosis.

DIFFERENTIAL DIAGNOSIS OF SCOURING IN CALVES AGED 4-10 W.O.Affected calves were all more than 4 weeks old soinfection with E. coli, Rotavirus or Coronavirus wasunlikely. Other common causes of scour for calves ofthis age are coccidiosis and cryptosporidiosis, thoughneither is generally associated with such severeclinical signs, rapid deterioration or high mortality asin this herd (Bazeley 2003). The incidence ofSalmonellosis as a cause of disease in calves isprobably higher than recognised, and in a UK surveyof diarrhoeic calves, salmonellae were isolated in 12%of sick calves and in 24% of outbreaks (Jones,Watsonand Wallis, 2004).

EPIDEMIOLOGYA number of salmonella serotypes cause disease incattle, although in the UK, S. Dublin and S.

HERD BACKGROUNDThis is a family farm run by father and son, with adairy herd of about 100 cows, average yield 7,000L.Heifer dairy calves are reared as replacements andsome beef calves are reared to be sold at weaning.Calves are reared in single pens to one week old thenmoved into groups of 5 in a barn next to the milkingparlour.

During 2005 two bulls were bought from differentfarms, and 6 heifers were bought from a neighbouras they calved in. No calves were purchased.

CLINICAL HISTORYSeven cows and one heifer aborted in a period ofnine weeks.Generally they were profoundly sick,withsevere milk drop (in some cases for 2-3 days beforeabortion), diarrhoea and pyrexia.The heifer died oneweek after abortion. Two freshly calved heifers alsobecame clinically ill. Calves began to scour about 4weeks after the first abortion and 7 of the 15 affectedcalves died within 1-2 days despite antibiotics,electrolytes and nursing. The calves that survivedremained extremely poor and failed to thrive.

DIFFERENTIAL DIAGNOSIS OF ABORTION IN COWSA low level (figures vary, but a target of less than 2%can be used) of foetal loss can be considered ‘normal’or unavoidable, but higher losses are caused by arange of infectious and non-infectious agents. Thecommon infectious causes of abortion and associatedclinical signs are listed in Table 1.

CATTLE l CLINICALUK Vet - Vol 11 No 5 September 2006 1

Katrine Bazeley BVSc BSc CertWEL MRCVSKINGFISHER VETERINARY PRACTICE, TOWER HILL ROAD, CREWKERNE, SOMERSET. TA18 8EQ

An outbreak of Salmonellosis in aSomerset dairy herd

Total cases where a diagnois was reached: 1111Total cases where no diagnosis was reached: 4614

Fig. 1: DEFRA Diagnostic results of ‘Fetopathy’ in2003.

typhimurium are by far the most common. Mosttransmission of disease occurs directly from animal toanimal, although it may also be transmitted viacontaminated feed, pasture spread with contaminatedanimal waste or human sewage sludge,or contaminatedwater. S. Dublin is a cattle-specific organism, and istherefore less likely to be spread by birds or rodents, asother serotypes may, although there is fairly goodevidence for local bird spread in SW Scotland. Infectedcattle shed vast numbers of organisms in the faeces.Adult cattle often become carriers of S. Dublin,

excreting the organism mainly at times of stress, forexample after sale or around calving. S. Dublin isoften harboured in the gall bladder and the disease issometimes associated with liver fluke infestation.

In this herd there was a history of introduction of apurchased heifer that had ‘calved early’; it is possiblethat this animal brought the disease with her. It isalso possible that this outbreak was simply the re-emergence of disease carried within the herd for aprolonged period.

CATTLE l CLINICAL UK Vet - Vol 11 No 5 September 20062

Agent Clinical signs Transmission Control measuresSalmonellae (various Abortion usually with high temperature, Carrier animals. Contaminated feed Strict hygiene. No purchased cattle. serotypes) severe depression, scour. May be high or water. Pasture spread with Vermin control. Vaccine (S. Dublin

mortality rates contaminated animal waste or human and S. typhimuriumIn calves, septicaemia, scouring and death. sewage waste. Birds and rodentsZOONOSIS

Brucella abortus Generally very high rate of abortion with Infected animals (in UK) Bulk milk monitoring +/- eradicated no other clinical signs. Cull of sero-positive stockfrom UK ZOONOSIS All cattle abortions must be reported

to DEFRA for brucellosis control

Neospora caninum May occur as outbreak of abortion. No Congenital infection of calves from Calving hygiene, feed hygiene. Can cull other clinical signs in cows. Infected infected mothers. Lateral spread congenitally infected cows (impossible if foetus may be mummified, still born, through aborted material, foetal incidence is high)premature live-born or clinically normal fluids etc. ?Role of intermediate carrier. May be repeated abortions in host (dog, fox)infected cows

Leptospira hardjo May or may not be milk drop and fever Via urine of infected animals (may No purchased cattleZOONOSIS continue to excrete for some months Prophylactic treatment of in-coming

post infection. Contaminated bullsabortion material and vaginal fluids. Mains water supplyThrough semen of infected bull Calving hygiene(not common) VaccinationContaminated water sources (rivers and streams)

Infectious Bovine May be no other clinical signs in aborting Infected carrier cattle No purchased cattleRhinotracheitis virus cattle. In all age groups may be fever, Hygiene at calving(IBRV or BHV1) upper respiratory tract infection, nasal Vaccination

and ocular discharges, secondarybacterial pneumonia

BVDV Aborting cows; usually no other clinical PI cattle (may be chronically unthrifty Early identification and cull of PIssigns. Rest of herd: early embryonic loss, or may be clinically normal) PI animals (antigen positive blood). Hygieneimmune suppression. Birth of congenitally are the result of in utero infection at Vaccinationinfected PI calves that later develop about 90-120 days’ pregnancymucosal disease. Congenital defects (cataracts and cerebellar hypoplasia)

Campylobacter foetus Early embryonic death and abortion. Venereal infection from carrier cows Don’t use hire bull. Identify infected bullPurulent vaginal discharge in affected to infected bull to uninfected cows (prepucial isolation). Treat/cull infectedcows and heifers. Normal fertility once and heifers bull. Difficult to identify carrier cowsimmune

Trichomonas foetus Abortion and infertility. Pyometra post Venereal infection as above AIabortion. Foetus may be macerated Introduce only virgin bulls into herd

No treatment for infected bulls

Listeria Abortion with or without septicaemia Soil organism. Infection generally via Avoid feeding spoiled silage. Removemonocytogenes CNS signs (fever, circling) – not usually in spoiled silage rejected silage. Avoid soil contamination

the same outbreak of silage as it is made

Bacillus licheniformis Generally no other clinical signs. May be Widespread in the environment. Antibiotic treatment for group may haveoutbreak of abortions Silage may support heavy loads of some effect

the pathogen

Mycoses e.g. Generally no other clinical signs. Aborted Fungal contaminated fodder e.g. hay Dry storage of fodder. Aspergillus fumigatus foetus may have raised cutaneous plaques. harvested in wet seasons. Avoid feeding mouldy hay and silage

TABLE 1: Differential diagnosis of common infectious causes of abortion in cattle in the UK

Once the adult cows were infected it was easy fordisease to spread to the young calves either viacontaminated milk, or spread on boots and clothing.

CONTROL MEASURES - IMMEDIATEIdeally, the following control measures should beadopted:1. Immediate investigation of the cause of abortion,

and early investigation of the cause of diarrhoea.2. Isolation of aborting cows and disposal and

disinfection of all aborted material and beddingcontaminated by affected cows

3. Institution of strict hygiene measures to controlspread of disease. These should include use ofseparate overalls and disposable gloves forhandling infected cattle and the use of a boot dipmade up to specified concentration and changeddaily.

4. Careful personal hygiene. Although S. Dublinrarely infects humans, it can cause serious disease.

5. Treatment for liver fluke

In this herd, cows were not kept fully isolatedfollowing abortion and a boot dip and other hygienemeasures were not put in place immediately and mayhave allowed spread of disease from cows to calves.There were no further cases in calves once theinfected animals were moved out and the house wasthoroughly cleaned and disinfected using FAM 30(an iodine-based chemical).

CONTROL MEASURES - LONGER-TERMIdeal:1. Stop buying in cattle

2. Alternatively, if cattle must be bought-in,quarantine for one month. Bacteriologicalinvestigation may or may not identify carrieranimals during this period

3. Keep feed in vermin-proof containers 4. Make sure that water sources are free from

contamination 5. Control liver fluke and other debilitating disease6. Calve cows in single pens and clean and disinfect

between occupants7. Ensure that all calves receive at least 2 litres of

colostrum within 6 hours of birth, and continueto be fed colostrum for a minimum of 24 hours.

8. All-in, all-out policy for calf-rearingaccommodation

9. Try to identify carrier cows by sampling threetimes on consecutive days at calving time

10. Vaccinate the herd.

In this herd, in-calf heifers have been vaccinated andwill continue to be vaccinated, on the basis that theheaviest losses are those due to abortion. Hygienelevels are good, and the situation will be reviewed.There has been no disease for three months. Thisimprovement may not be the result of vaccination.

COSTS OF DISEASELosses continued for approximately two monthsafter the first cow aborted.

According to these calculations (Tables 2 and 3),total costs of the outbreak to date: £7869.33p.

CATTLE l CLINICALUK Vet - Vol 11 No 5 September 2006 3

Cost per animal affected Number affected Total herd costLoss of aborted foetuses = 0.5 x £75 8 £600value of heifer calf (assuming half are female)

Retained foetal membranes £265.41* 1 £265.41(average 70% post abortion)

Milk lost** 19,430L @ 18.5ppL £3596.40

Subsequent fertility (not likely 0to be affected) No figures yet, but all cycling normally, some already served

Death of cow (cost of replacement) £900 1 £900

Diagnostic testing £163

Veterinary treatment (no charge £357for DEFRA abortion enquiry visits)

Vaccine cost £3.77 £452.52

Farmer time (estimate) 15 mins per day for 28 days @ £10 per hour £70

Total £6395.33

* Cost of RFM taken from Esslemont R.J. (2003). 1997 DAISY figures** Loss of yield was calculated using individual NMR projected yields for this lactation, and last lactation yield if available, or average yield for that

lactation if individual yield is not available.Loss in yield = 66,317 - 42,887

= 19,430litres

TABLE 2: Costs of disease - abortion

CONCLUSIONThis disease, despite early investigation and vigoroustreatment, has caused significant losses that maycontinue.

CATTLE l CLINICAL UK Vet - Vol 11 No 5 September 20064

REFERENCES

ANDREWS A. H. (2000) Cattle Practice Calf Pneumonia Costs pp109-114.

BAZELEY K. J. (2003) In Practice Investigation of diarrhoea in the

neonatal calf pp152-159.

CALDOW G. (2002) Cattle Practice 10:4 Cattle Abortion: what

samples when? pp 269-274.

ESSLEMONT R. J. (2003) Cattle Practice The Costs of Poor fertility and

What to do About Reducing Them. pp237-250.

JONES P. W., WATSON P. R. and WALLIS T. S. (2004)in Bovine

Medicine 2nd edition ed Andrew A. H., Blowey R. W., Boyd H. and Eddy

R. G. pp231-238.

Cost per animal affected Number affected Total herd cost

Death of bull calves £0 1 £0

Death of heifer calves £150 6 £900

Reduced growth £27 *** 8 £216

Diagnostic testing £85

Veterinary treatment £133

Farmer time (estimate)

30 mins per day for 28 days @ £140£10 per hour

Total £1474

*** This is a rough estimate and may be an underestimate. Affected calves were still very poor at time of writing. Possibly some may never recover to become replacement heifers. Cost of weight loss in calves taken from A. H Andrews (2000).

TABLE 3: Costs of disease - diarrhoea