Brucellosis
Brucella melitensis, Brucella abortus, Brucella suis, Brucella canis
Occurrence
Brucella melitensis and Brucella abortus are common in domestic and farm animals worldwide with regional differences. In 2018, an outbreak caused by B . melitensis was reported in a cattle herd in Upper Austria. B. suis (Biovar 2) is rarely detected in domestic pigs and humans in Europe. Disease outbreaks were last detected in 2017 and 2024 in breeding sow farms in Upper Austria. B. canis was first detected in Austria in 2010 as an abortus pathogen in dogs on a poodle breeding farm in Upper Austria.
Pathogen reservoir
Cattle, sheep, goats, wild boar, hare, dog. The pathogen reservoir of B. abortus is cattle, and longstanding control programs have eradicated the pathogen in our latitudes. In the USA, infected wild bison herds are occasionally found, and in developing countries this pathogen is more common in humans and animals. The species B. melitensis occurs primarily in sheep and goats in Mediterranean countries. Wild boar and brown hares act as reservoirs for Brucella suis Biovar 2.
Infection route
Transmission to humans usually occurs through food containing Brucella (raw milk and products made from it) or through direct contact with infected animals and their excretions. Direct transmission from person to person is extremely rare (in individual cases through breastfeeding or blood transfusions). The risk of infection in Austria is very low.
Symptoms
Up to 90 per cent of all infections are asymptomatic. They can only be detected by testing for specific antibodies in patients and are a sign of a successful immune response. In the early stages of acute brucellosis, non-specific, flu-like symptoms occur, such as tiredness, a slight fever, and headaches and aching limbs. After a brief, symptom-free interval, flu-like symptoms may reappear, often accompanied by evening spikes in temperature of up to 40 °C, combined with profuse sweating; in the morning, the temperature frequently returns to normal levels. Self-limiting courses of the disease (i.e. a resolution of symptoms without antibiotic treatment) are possible, but carry the risk of a chronic course with recurrent episodes of fever.
Food-borne disease outbreaks
In 2025, there were no reported foodborne disease outbreaks in Austria caused by Brucella. In both 2019 and 2020, one outbreak each caused by B. melitensis was investigated; these were likely due to the consumption of raw milk and sheep meat whilst abroad.
Food
Due to the officially recognized brucellosis-free status of the Austrian cattle population as well as the sheep and goat population, foodstuffs are currently not tested for brucella in Austria. In 2021, no foodborne disease outbreak (LMbKA) caused by brucella was notified to the EMS in Austria (as of March 1, 2022). In each of 2019 and 2020, one outbreak caused by B. melitensis was reported, probably due to consumption of raw milk and sheep meat abroad.
Animal
Bovine brucellosis: In Austria, the cattle population was officially recognised as free from brucellosis (OBF) as early as 1999. In 2008, the Brucellosis Testing Regulation came into force. Until 2012, comprehensive monitoring of all dairy cattle holdings was carried out via tank milk testing, whilst blood tests were conducted in accordance with a risk-based sampling plan. Since 2013, bulk milk samples from milk-supplying holdings have also been selected in accordance with a risk-based sampling plan. In 2025, pooled milk samples from 1,224 holdings were analysed. Tank milk samples that tested serologically positive were verified by means of blood samples. Blood samples from 1,328 non-milk-supplying cattle holdings were tested.
Brucellosis was not detected in any cattle herd. Austria’s cattle population has ‘disease-free’ status with regard to infections with Brucella abortus, B. melitensis and B. suis.
Sheep and goat brucellosis: Austrian sheep and goat herds were officially recognised as free from B. melitensis (OBmF) in 2001. To maintain this status, annual proof must be provided that fewer than 0.2% of all sheep and goat herds are infected with ovine and caprine brucellosis. In 2025, 1,661 sheep and goat herds were tested across the whole of the country in accordance with a risk-based sampling plan. There was no evidence of Brucella infections in sheep and goats. The Austrian sheep and goat population retains ‘disease-free’ status with regard to infections with Brucella abortus, B. melitensis and B. suis.
Human Medicine
Direct transmission from person to person is extremely rare (in individual cases through breastfeeding or blood transfusions) and occurs only in exceptional cases. It has essentially only been observed in infants through the milk of infected mothers. Brucella can be transmitted directly through contact with diseased animals or indirectly through contaminated food. Bovine brucellosis is enzootic in the herd. It poses a risk to human health, particularly to those in direct contact (farmers, veterinarians, slaughterhouse staff). Raw milk (unpasteurised milk or products made from it, such as butter made from raw milk and raw milk cheese) and raw meat from infected animals pose the greatest risk of transmission. In addition to the gastrointestinal tract, the pathogen can be absorbed into the body by several other routes, including the conjunctiva, the respiratory tract and injured skin. After entering the body, brucella are taken up by cells of the monocyte-macrophage system and transported to the nearest lymph nodes. From the infested lymph nodes, the germs are disseminated first lymphogenically and then hematogenically, reaching most organs, especially the liver, spleen, and bone marrow. In the affected organs, inflammatory granulomas consisting of macrophages and lymphocytes can form due to the activation of specific T cells. From these inflammatory foci, the brucella can enter the bloodstream in spurts.
Symptoms
The incubation period of brucellosis is usually 1 to 2 months (incubation periods of 5 days to 150 days have been described in individual cases). Up to 90% of all infections are subclinical; they can only be identified by the detection of specific antibodies in the patient and are an expression of a successful immune response. In acute brucellosis, fatigue, mild fever, headache and pain in the limbs occur in the initial phase. After a short, symptom-free interval, flu-like symptoms may appear, which then do not stop after 7 to 10 days as is usual with influenza. Typical for brucellosis are evening temperature rises of up to 40 °C combined with massive sweating! The temperature returns to normal in the morning. This undulating fever is typical of brucellosis in humans. The phases last up to 5 weeks and are interrupted by remission periods of up to 2 weeks with greatly attenuated symptoms. The course of fever extends over 7-21 days and may be interrupted by 2- to 5-day fever-free intervals (undulating fever). Chronic courses of the disease can lead to complications in the nervous system and internal organs. The disease can be treated well with antibiotics.
Specialist Information on Veterinary Medicine
The genus Brucella comprises 12 officially described species: Brucella abortus, Brucella suis, Brucella melitensis, Brucella canis, Brucella ovis, Brucella neotomae, Brucella ceti, Brucella pinnipedialis, Brucella microti, Brucella inopinata, Brucella papionis and Brucella vulpis.
In Austria, the cattle population has been officially recognised as free from bovine brucellosis since 1999, and the sheep and goat populations have been officially recognised as free from ovine and caprine brucellosis since 2001; therefore the risk of infection in humans in Austria is very low. The most recent outbreak caused by B. melitensis was detected in 2018 in a cattle herd in Upper Austria.
Cases of disease in domestic pigs caused by B. suis biovar 2 are rarely reported in Europe. In Austria, swine brucellosis was first detected in Styria in the 1990s in a breeding sow. In 2003, outbreaks occurred at several pig farms in the Waldviertel region of Lower Austria, and in 2004 there was an outbreak in the district of Schärding in Upper Austria. In 2017, an outbreak was detected at a breeding farm in the district of Grießkirchen in Upper Austria, involving a total of nine contact farms; in 2024, an outbreak occurred at a breeding sow farm in Upper Austria.
B. suis biovar 2 is widespread in Europe amongst wild boar and hares and can be transmitted from these wild animals to domestic pigs and humans. Of 228 wild boars hunted in 2011/2012 and examined from 8 districts in Upper Austria, Lower Austria and Burgenland, B. suis biovar 2 was isolated from the head lymph nodes of 12 animals (5.2 per cent). Intermediate hosts of B. suis biovar 2 include humans, cattle, dogs, rats, red foxes and roe deer. The red fox can serve as an indicator species for the investigation and monitoring of natural brucellosis foci (B. suis, B. microti, B. vulpis). Between June 2007 and July 2008, mandibular lymph nodes from 903 foxes from 37 districts (20 in Lower Austria, 5 in Burgenland, 5 in Upper Austria and 7 in Styria) were examined, during which B. suis foci in Lower Austria, Styria and Burgenland were identified. In 2024 and 2025, Brucella suis biovar 2 was detected in brown hares in Carinthia and Styria respectively. Whilst B. suis biovar 2 has only low pathogenicity for humans (rare reports, patients with pre-existing conditions), B. suis biovar 1 – which, in Europe, has so far only been detected in wild and domestic animals in Croatia – is highly pathogenic to humans.
B. microti is a newly described species that was first detected in 2000 in the Czech Republic in infected field mice and, in 2007, on several occasions in Lower Austria in foxes. The pathogenic significance of this causative agent of murine brucellosis for other animals and humans is unclear. To date, this species has only been detected in wild animals in the Czech Republic, Austria and Hungary. In 2025, the pathogen was isolated for the first time from sheep and goats in France.
B. vulpis was officially described as the twelfth Brucella species in 2016. To date, this species has only been isolated in Austria. In 2008, this Brucella species was isolated in the Hollabrunn district of Lower Austria from macroscopically normal mandibular lymph nodes of two foxes. The reservoir of this pathogen and its pathogenic significance for other animal species and humans is unclear.
B. canis was first detected in Austria in 2010 as a cause of abortion in dogs at a poodle breeding kennel in Upper Austria and is also a zoonotic pathogen. Sporadic cases, particularly in dogs with a relevant travel history, occur from time to time.
B. ovis, the causative agent of infectious epididymitis in rams, is not pathogenic to humans.
Transmission and symptoms
Epidemiologically significant massive shedding occurs particularly during abortions and in infected live births, but also via milk, urine, faeces and nasal secretions. Typical routes of infection are oral ingestion and transmission during mating. Infection via the skin, including via arthropods acting as vectors, must be considered.
Domestic pigs: In endemic areas, there is a risk of transmission of B. suis biovar 2 from wild animals to domestic pigs, particularly where domestic pigs are reared outdoors. However, the pathogen can also be introduced via contaminated forage, indirectly via carnivorous mammals such as foxes and dogs or scavenging birds, or through the purchase of a chronically infected boar for a breeding sow herd. The improper disposal of animal by-products from hunted wild boar and hares also poses a risk of exposure to hunting dogs involved in the hunt and to the livestock population. Adherence to basic hygiene principles during hunting and the processing of game by hunters is the most important measure for preventing the introduction of the pathogen into domestic pig herds and its transmission to humans.
Within a domestic pig herd, infection occurs primarily through contact with infected material such as aborted foetuses, afterbirths, bodily excretions and secretions, and during mating. The incubation period varies greatly (from a few days to several months). In the event of infection via mating with an infected boar, the first symptom to appear after 5–8 weeks may be frequent miscarriages resulting from early abortions. However, abortions can occur at any stage of pregnancy. In domestic pigs, a new outbreak in sows leads to frequent abortions at all stages of pregnancy, the birth of weak piglets, retained placenta and uterine inflammation, possibly with small nodular lesions. In boars, testicular swelling and inflammation may occur. In general, mobility problems due to joint inflammation and abscess formation in various organs may develop. The disease, characterised by years of pathogen shedding, may also progress without clinical signs.
Cattle: Prior to the frequent abortions, the infection is usually asymptomatic apart from a temporary rise in temperature. The animals remain shedding the pathogen. Calving in the second half of gestation is the most noticeable symptom; as a rule, no signs of the disease are observed prior to abortion. This is often followed by inflammation of the joints, tendon sheaths and bursa; clinically apparent mastitis is less common (pathogen shedding!). Following an abortion, a cow may well go on to carry a normal calf to term; a subsequent calving is just as possible as infertility following the first abortion. In bulls, inflammation of the testicles and epididymis is observed. Bovine brucellosis is enzootic within a herd. Infections with B. abortus rarely occur in other animal species (sheep, goats, pigs). Their occurrence is usually attributable to contact with infected cattle herds.
Sheep and goats: Brucellosis in sheep and goats is primarily caused by B. melitensis and its three biovars. The clinical course is similar to that of bovine brucellosis. In animals, this frequently leads to cases of abortion, the birth of weak lambs and inflammatory changes, particularly in the reproductive system. In addition, mastitis and inflammation of the testicles and epididymis occur. In rams, brucellosis also occurs in the form of infectious unilateral and bilateral epididymitis, accompanied by a deterioration in sperm quality, caused by Brucella ovis. Brucellae are transmitted during mating and can lead to abortions in the ewe. Following colonisation of the kidneys, the bacteria are excreted in the urine.
Dogs: Infected dogs do not develop a fever and may remain bacteraemic for years. Serological tests may yield false-negative results despite the presence of bacteraemia. Brucellosis may go undetected if clinical symptoms are absent or fail to be recognised (infertility, pregnancy complications, iritis, spondylodiscitis, lymphadenitis, prostatitis, epididymitis).
Control/Prevention
Brucellosis in cattle, pigs, sheep and goats is a notifiable animal disease. Control measures focus on the early detection, isolation and systematic culling of infected animals, as well as the control of animal movements to prevent the spread of the pathogen. Monitoring to ensure the absence of the disease is carried out through serological testing.
In accordance with the European Animal Health Law (Regulation (EU) 2016/429) and Delegated Regulation (EU) 2018/1882, infections with Brucella abortus, Brucella melitensis and Brucella suis in cattle, sheep and goats are listed as Category B, D and E animal diseases. This classification requires active control and long-term eradication. Classification in Category D also requires controls on trade and transport, which also apply to pigs, camelids and cervids. Infections in carnivores and lagomorphs are classified as Category E and are subject to mandatory reporting.
For farmers, vets, livestock breeders and slaughterhouse staff, the consistent implementation of biosecurity and hygiene measures when handling infected animals is essential. In particular, changing clothes and footwear after working in the barn, wearing protective gloves when assisting with births, and cleaning and disinfecting equipment and hands play a key role in preventing the spread of the pathogen and safeguarding animal health in the long term.
Diagnosis
For the detection of brucellosis in cases of abortion, the placenta is a particularly important sample for diagnostic purposes due to the high concentration of the pathogen. As certain Brucella species are classified as risk group 3 pathogens, their cultivation and phenotyping may only be carried out in a biosafety level 3 (BSL-3) laboratory, namely the Centre for Biological Safety at the National Reference Laboratory for Brucellosis in Mödling. The precise identification of the isolated Brucella species is carried out both phenotypically, using conventional bacteriological methods, and molecularly, using a species- and biovar-specific multiplex PCR. Direct tissue PCR enables rapid detection of the pathogen at genus level. The serological detection of specific antibodies is also a diagnostic parameter.
Contact
Leitung
Priv.-Doz. Mag. Dr. Alexander Indra
- humanmed.wien@ages.at
- +43 50 555 37111
-
Währingerstraße 25a
1090 Wien
Institut für veterinärmedizinische Untersuchungen Mödling
- vetmed.moedling@ages.at
- +43 50 555 38112
-
Robert Koch-Gasse 17
2340 Mödling
Last updated: 11.08.2026
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