Bovis ISSN 2398-2993

Brucellosis

Synonym(s): Contagious abortion, Bang's disease, Undulant fever

Contributor(s): Tracy Anderton, Mike Reynolds

Introduction

  • Cause: bacteria from genus Brucella; it is mainly Brucella abortus that causes disease in cattle, but in some regions, Brucella melitensis is the main causal agent.
  • Brucella suis has occasionally been isolated from cattle but does not appear to cause disease or be spread between individuals.
  • Signs: reproductive failure: abortion, premature calvings, reduced milk production, reduced weight gain
  • Diagnosis: serology, culture of bacterium from milk or vaginal swab.
  • Treatment: legislation and eradication policies in many countries means that treatment is often forbidden. In those countries where treatment is allowed, oxytetracycline and streptomycin may be considered.
  • Prognosis: dam lives and will go on to have live offspring but may keep shedding the bacteria.

Pathogenesis

Etiology

  • Bacteria from genus Brucella; mainly Brucella abortus Brucella abortus in cattle. Brucella melitensis can be the causal agent in some regions of the world.
  • Main source of infection is from bacteria present in high levels in the aborted fetus, birth fluids and placenta.
  • Bacteria is also shed in milk and semen.
  • B. abortus can survive in the environment for several months, especially if it is cool and moist and will still be infectious.
  • There are wildlife reservoirs of bacteria, ie hare, bison, elk, feral pigs. This is a risk to cows but can complicate eradication efforts.

Predisposing factors

General

  • The primary source of Infection is the spread of infection from one animal to another, particularly at parturition.
  • In a naïve herd, this spread of infection may cause many animals to become infected and abortion storms to occur Abortion & stillbirths overview.

Pathophysiology

  • Infection occurs naturally by ingestion.
  • Initially, B. abortus is found in the regional lymph nodes and then invades the blood stream causing a bacteremia.
  • The bacteria then spread to colonize the supramammary lymph nodes, the mammary gland, the gravid uterus and placenta.
  • This causes the effects associated with the disease: placenta disruption, fetal death and contamination of milk.

Timecourse

  • The fetus is often retained for up to 3 days before being expelled.
  • Numerous bacteria are expelled from the genital tract at parturition and can continue to do so for up to 3 weeks following abortion.
  • Some cows which have previously aborted due to infection, will continue to shed brucella from their reproductive tract at subsequent, normal parturitions.
  • The organism is shed for a variable length of time in milk and may occur intermittently for the rest of that animal’s life.

Epidemiology

  • The main source of Infection is the spread of infection from animal to another, particularly at parturition. In a naïve herd, this spread of infection may cause many animals to become infected and abortion storms to occur
  • The disease is notifiable in the UK - all abortions must be reported to the APHA. In this way, an animal (and hence a herd) that is positive for B. abortus is identified. Measures are then taken to ensure spread does not occur to another premises.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Franc K A, Krecek R C, Hasler B N & Arenas-Gamboa A M (2018) Brucellosis remains a neglected disease in the developing world: a call for interdisciplinary action. BMC Pub Health 18 (125) BMCPubHealth.
  • Lalsiamthara J & Lee J H (2017) Development and trial of vaccines against Brucella. J Vet Sci 18 (S1), 281-290 PubMed.
  • Dorneles E S, Sriranganthan N & Lage A P (2015) Recent advances in Brucella abortus vaccines. Vet Res 46, (76) VetRes.
  • Millar M & Stack J (2012) Brucellosis - what every practitioner should know. In Pract 34 (9), 532-539 BMJ.

Other sources of information

  • Martin A (2009) Bovine Abortion Prevention. Vet Times. Website: www.vettimes.co.uk.
  • Smith B P (1990) Large Animal Internal Medicine. 2nd edn. pp 1405-1406.
  • Animal & Plant Health Agency (online) Official Veterinary Instructions – Brucellosis. Website: http://apha.defra.gov.uk.
  • APHIS (online) Facts About Brucellosis. Website: www.aphis.usda.gov (pdf download).
  • Centers of Disease Control and Prevention (online) Brucellosis. Website: www.cdc.gov/brucellosis.
  • Department of Agriculture, Environment and Rural Affairs (online) Brucellosis. Website: https://www.daera-ni.gov.uk.
  • Millar M & Aggett D (online) Brucellosis outbreak in cattle in Kenya and surveillance in Britain. Vet Times.

Organisation(s)


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