HAIRS risk assessment: Brucella canis

Question 1

About the Human Animal Infections and Risk Surveillance group

Accepted Answer

This document was prepared by the UK Health Security Agency (UKHSA) on behalf of the joint Human Animal Infections and Risk Surveillance (HAIRS) group.

HAIRS is a multi-agency cross-government horizon scanning and risk assessment group, which acts as a forum to identify and discuss infections with potential for interspecies transfer (particularly zoonotic infections).

Members include representatives from:

UKHSA
the Department for the Environment, Food and Rural Affairs (Defra)
the Department of Health and Social Care (DHSC)
the Animal and Plant Health Agency (APHA)
the Food Standards Agency
Public Health Wales
Welsh Government
Public Health Scotland
Scottish Government
Public Health Agency of Northern Ireland
the Department of Agriculture, Environment and Rural Affairs for Northern Ireland
the Department of Agriculture, Food and the Marine, Republic of Ireland
Health Service Executive, Republic of Ireland
Infrastructure, Housing and Environment, Government of Jersey
Isle of Man Government
States Veterinary Officer, Bailiwick of Guernsey

Version control

Date of this assessment: August 2023

Version: 1.0

Reason for the assessment: Since summer 2020, there has been an increasing number of reports of Brucella canis infection in dogs; the majority of which have been directly imported into the UK from Eastern Europe.

This risk assessment provides a qualitative description of the current risk to the UK human population, highlights gaps in evidence and provides recommendations for mitigating the public health risk.

Completed by: HAIRS members and external experts

Non-HAIRS group experts consulted:

John McGiven, Brucellosis disease consultant, Animal and Plant Health Agency
Alessandro Gerada, Consultant Medical Microbiologist, Brucella Reference Unit

Date of initial risk statement: February 2021

Information on the risk assessment processes used by the HAIRS group can be found on GOV.UK.

Question 2

Summary

Accepted Answer

Historically, Brucella canis (B. canis) has not been regarded as endemic in the UK. Since summer 2020, there has been an increase in the number of reports of B. canis infection in dogs, the majority of which have been in dogs directly imported into the UK from Eastern Europe. B. canis is a recognised zoonotic pathogen, but human cases are rarely reported globally; most likely due to the non-specific nature of infection, generally mild symptoms, lack of validated serology tests and because it is generally acknowledged to be less virulent to humans than other members of the Brucella genus, for example, B. abortus, B. melitensis and B. suis.

As of July 2023, 2 laboratory-confirmed cases of B. canis human infection have been identified in the UK. One case was identified from clinical suspicion after presenting at hospital. A second case had no clinical symptoms, worked at a veterinary practice and was identified through the follow-up of individuals exposed to positive dogs. In both incidents, the implicated dogs were not known to be infected at the time of human exposure, but subsequently tested positive.

Based on the available evidence, individuals at greatest risk of exposure to B. canis are those who have contact with B. canis contaminated materials, especially fluids and tissues associated with breeding and parturition, either in an occupational or domestic setting. The potential impact of human B. canis infection may be greatest for those who are immunocompromised or have underlying health concerns.

Assessment of the risk of infection in the UK

Probability

The probability of infection would be considered Very Low for the general UK population.

The probability of infection for individuals with greater risk of exposure to infectious material from B. canis infected dogs (for example dog breeders, kennel, veterinary and laboratory staff and owners of infected dogs, especially those which are breeding or birthing) would be considered Low.

Impact

The impact on the UK population would be considered Very Low to Low. Severe disease associated with B. canis infection has been reported, and immunocompromised individuals may be at higher risk of severe infection. There is, however, a lack of evidence to determine specific risk factors which contribute to disease severity and/or poorer clinical outcomes, as well as a paucity of evidence and understanding around the long-term impact of sequelae from infection and potential recrudescence.

Level of confidence in assessment of risk

Satisfactory.

Evidence gaps

Lack of systematic surveillance for disease in dogs in most countries, resulting in an incomplete understanding of which countries are endemic, and the prevalence levels in their respective dog populations.

Disease in the UK is still principally associated with imported dogs and their canine contacts and/or offspring. It is not known if the disease has yet reached a low level of regional endemicity in the UK dog population.

Potency of non-reproductive routes of transmission between dogs and the extent to which neutering dogs reduces risk of non-reproductive transmission of B. canis (and reduces susceptibility of infection).

There are relatively few reports of human B. canis cases globally, resulting in a lack of knowledge about specific risk factors for contracting infection and for severe disease.

Whether subclinical infection in humans warrants follow up and/or treatment.

Whether there is any difference in virulence between B. canis strains.

Long term effects of untreated B. canis infection in humans and dogs.

Long term effects, if any, of subclinical infection in humans.

Implications of repeated exposure particularly in an occupational setting, and whether recurrent infection is a possibility or if there is protective immunity after infection.

Accuracy and international validation of diagnostic testing for humans.

Significance of reactive laboratory tests in humans following exposure but in the absence of any symptoms.

Accuracy of blood culture methods for dogs (and the potential difference in sensitivity between puppies and adults).

Degree of harmonisation of diagnostic methods (and extent of differences in diagnostic accuracy).

Potential difference in serodiagnostic accuracy for adult dogs versus puppies.

Possible causes of serological false positive reactions (and which organisms may do this).

Efficacy of antibiotic treatment in dogs and uncertainty with respect to whether new treatments (or treatment combinations) may be more effective.

Extent to which antibiotic treatment may help to drive emergence of antibiotic resistant strains of B. canis (and other non-Brucella bacteria which may be present).

Lack of established and effective risk mitigation measures in veterinary practices.

An understanding of the level of awareness and knowledge about B. canis amongst dog breeders, importers, charities and vets.

Ability of B. canis to survive in the environment – unlike other Brucella species, B. canis field strains are largely mucoid forms.

Actions and recommendations

Individuals with a greater exposure risk (such as veterinary professionals and those in contact with potentially infected dogs) and/or susceptibility to infection (for example immunocompromised individuals who are at risk of exposure) should be informed of the risks and health impacts of B. canis infections, as well as how suspect dogs can be diagnosed within the UK.

Encourage dog breeders, charities or organisations importing dogs from B. canis endemic countries to ensure effective pre-export testing is performed and that dogs subsequently imported into the UK are negative to this.

Breeders should consider the risk of B. canis and the testing of any newly introduced dog that will be used for breeding.

Encourage private pre-breeding tests if appropriate, in particular where there are risk factors for infection present, with sampling by the Private Veterinary Surgeon.

To highlight to veterinary professionals the risk of B. canis infection in dogs from known endemic countries.

The risk of B. canis infection in imported dogs from endemic countries should be highlighted to potential owners, especially those assessed to be at greater risk of infection, as well as advice given on recommended veterinary management for test positive animals.

If an imported dog with clinical signs suggestive of a possible B. canis infection is presented to a vet, staff attending the case should use appropriate personal protective equipment (PPE), and consider appropriate sampling and submission to laboratories for testing.

Veterinary staff should warn laboratory staff when B. canis is suspected (particularly for imported dogs) to ensure appropriate precautions are used in the laboratory to prevent exposure of laboratory staff.

When a positive B. canis canine result is obtained, further consideration should be given to the appropriate management of the risk to human health. Detailed advice on this will need to be made available on government websites.

Advice needs to be given to the veterinary community about the level of risk presented by B. canis and effective and proportionate risk mitigation measures. This should be done in consultation with the Health and Safety Executive as the Advisory Committee for Dangerous Pathogens currently classify B. canis as a hazard group 3 human pathogen.

Question 3

Step 1: Assessment of the probability of infection in the UK human population

Accepted Answer

This section of the assessment examines the likelihood of an infectious threat causing infection in the UK human population. Where a new agent is identified there may be insufficient information to carry out a risk assessment and this should be clearly documented. Please read in conjunction with the probability algorithm (Annexe A).

Is this a recognised human disease?

Outcome

Yes.

Quality of evidence

Satisfactory.

Background

Brucella species have a global distribution, and while most of these species have a host preference, they have the ability to infect many mammalian species. Several Brucella species are pathogenic to humans, including:

B. melitensis (principally seen in goats, sheep and camels)
B. suis (pigs)
B. abortus (cattle)
B. canis (dogs)
B. ceti and B. pinnipedialis (marine mammals)

Brucellosis is rarely fatal in humans, with the greatest risk of morbidity and mortality associated with B. melitensis. Members of the Ochrobactrum genus, which are primarily opportunistic pathogens, have been assigned to the Brucella genus based on genetic similarity, but are not considered causes of human or animal brucellosis (1).

B. canis is principally viewed as an infection of dogs, although other UK-living carnivores such as cats and foxes may be able to be infected if in close contact with an infected dog or its immediate environment (2). B. canis is a recognised zoonotic disease, and human infections can occur through direct contact with contaminated secretions from infected dogs, or as a result of laboratory exposure particularly to bacterial culture (3 to 5).

B. canis infection in humans can be asymptomatic (4) or present with non-specific symptoms ranging from fever, headache, malaise, myalgia and weight loss to severe illness and complications including (rarely) endocarditis, osteomyelitis, arthritis, meningitis and septicaemia (5, 6). It can take months, even years, before symptoms develop in chronically infected individuals (7). Although B. canis-produced clinical disease in humans is similar to that caused by other Brucella species, it is generally not as severe. There have been no documented reports of B. canis associated fatalities in humans.

Human infection with B. canis is infrequently reported in the scientific literature. Given the generally mild and non-specific nature of human infections and the lack of validated tests for B. canis infection in humans, cases are likely under-reported globally (8). Diagnosis of B. canis infection is challenging due to the lack of highly specific and sensitive diagnostic assays. In the UK, there are no validated human serology tests for B. canis.

Is the disease endemic in humans within the UK?

Outcome

No.

Quality of evidence

Good.

Human cases of brucellosis (in other words, infection with any of the Brucella species) are rarely reported in the UK (less than 25 annually in the last decade); the majority of which can be attributed or presumed to be due to exposure outside the UK (9).

A previous epidemiological review of canine cases identified between summer 2020 and December 2021, found that more than 350 human contacts of confirmed and probable B. canis canine cases were risk assessed. Over 220 of these human contacts had occupational exposures, including veterinary (186 individuals) and laboratory (39 individuals) staff. Approximately 110 were identified as household contacts of a B. canis infected dog. Overall, almost 60 of all identified human contacts were risk assessed as having a high-risk exposure and none were confirmed as being infected with B. canis.

Since summer 2020, human testing for B. canis has been carried out in the UK, primarily after known high risk exposure to B. canis infected dogs. As of May 2023, over 400 human serum samples have been tested for B. canis, from individuals who were assessed as having a known exposure (including high-risk exposures such as direct contact with birth products from infected dogs or exposure to laboratory cultures).

As of July 2023, 2 laboratory-confirmed cases of B. canis human infection have been identified in the UK. One case was identified from clinical suspicion after presenting at hospital. A second case had no clinical symptoms, worked at a veterinary practice and was identified through the follow-up of individuals exposed to positive dogs. In both incidents, the implicated dogs were not known to be infected at the time of human exposure, but subsequently tested positive.

The nonspecific nature of symptoms associated with B. canis infection in humans, coupled with a low index of suspicion by physicians, and the inability of standardised serological tests for human brucellosis to detect infection with B. canis, may result in under-ascertainment of human cases within the UK.

Is the disease endemic in animals within the UK?

Outcome

No.

Quality of evidence

Satisfactory.

B. canis has a wide geographical distribution and is known to be endemic in the Americas, parts of Asia, Africa and eastern or central Europe (2). B. canis has historically not been regarded as endemic in the UK, and in the past has been very infrequently reported in dogs imported from endemic countries (10 to 13), with only 3 cases confirmed by APHA prior to 2020, all in imported dogs.

Pre- or post-import testing of dogs for B. canis is currently not required, so identification of B. canis infection in dogs in the UK has usually followed clinical disease, either through non-specific bacterial culture investigations or, through specific B. canis testing if the veterinarian is sufficiently aware of the disease.

As of February 2021 in England, and April 2021 in Scotland and Wales, B. canis was made a reportable animal pathogen if identified in a dog in the UK. In Northern Ireland, B. canis is listed as a notifiable disease under the Specified Diseases (Notification) Order (Northern Ireland) 2004, and therefore it is either reportable or notifiable in dogs throughout the UK.

No national surveys of the UK dog population for B. canis have been undertaken to permit UK prevalence to be estimated. Requirements by certain countries for pre-export testing of UK dogs for brucellosis mean that some testing (around 1,100 submissions for serological testing per year) of dogs has been undertaken by APHA. Given the high test specificity (0.99), this provides high confidence (95%) that there is less than 0.05% prevalence in the population of UK dogs.

The incubation period in dogs (excluding puppies) is between 2 and 12 weeks, after which seroconversion is detected. The clinical signs of B. canis infection in dogs are not pathognomonic, and infection can be subclinical. The most common clinical signs of B. canis infection in dogs are reproductive failure (in entire dogs and bitches), as well as lameness, back or joint pain.

Antimicrobial treatment is often unsuccessful at clearing infection from affected dogs due to the ability of B. canis to sequester intracellularly for long periods and cause episodic bacteraemia (8). Even following apparently successful antimicrobial treatment, it is impossible to confirm an animal has eliminated infection, and it is not possible to say that it no longer presents a risk of onward infection. Thus, euthanasia of infected dogs is considered the only way to completely remove the risk of future onward transmission.

The decision to euthanise is a matter for the owner(s) and their private veterinary surgeon and their willingness to accept the residual risks, which will vary on a case-by-case basis, if this course of action is not taken. If an infected animal is not euthanised, the dog may be neutered and concurrently treated with a course of antimicrobials. However, veterinary surgeons and their teams should take appropriate risk mitigating procedures if following this course of action (for example, the use of appropriate PPE). Reduction of the number of Brucella cells in the animal tissue will reduce the risk to the vet at the time of surgery and continuing the antimicrobial course post-operatively suppresses any potential recrudescence of infection in the dog due to the stress of the surgery.

Even if infected dogs are treated and neutered, the only way to ensure B. canis is not spread to other animals is to prevent close physical contact with other dogs or sharing of environments. However, the elimination of the reproductive routes of infection will remove the most significant means of disease transmission to dogs and people. Infected dogs, even if treated, may still be at risk of recrudescence of infection at any point and should be reviewed and tested by their veterinary surgeon if they develop clinical signs commensurate with B. canis infection.

The first 2020 B. canis incident was identified at a premise in south west England with over 20 dogs, of which some were used for breeding. Diagnosis, initially via serology but subsequently confirmed by bacterial culture from fresh abortion material, was made after several abortions had occurred in the preceding months and years. Subsequent serological testing identified that all remaining dogs at the site were positive via at least one test method – either serum agglutination test (SAT), rapid slide agglutination (RSA) test and indirect enzyme-linked immunosorbent assay (iELISA). Although some of the dogs present were imported, epidemiological investigations could not conclude definitively that any of these specific imported dogs were the index case.

Other dogs present (all serologically positive) were UK-born, but whether they had been used for breeding elsewhere and so brought the infection onto the premises is not clear. The wide spread of canine infection in this incident was probably due to the exposure of all dogs to highly infectious abortion material. This incident was also the first time dog-to-dog transmission of B. canis had been identified in the UK (14). Since this, there have been more incidents of dog-to-dog transmission within a household, but almost all with a direct association with an imported dog.

Are there routes of introduction into animals in the UK?

Outcome

Yes.

Quality of evidence

Good.

Infrequent and sporadic reports of diagnoses in imported dogs from several countries suspected of being endemic have been received by APHA in recent years. Some of these cases have been reported to the UK veterinary profession via letters to the Veterinary Record (10 to 13). Since July 2020, an increasing number of suspect canine cases of B. canis have been reported by private veterinarians and/or veterinary laboratories to APHA. Initially, such reports followed clinical suspicion which led on to laboratory identification (bacteriology, serology or polymerase chain reaction (PCR)), and tracings of littermates. However, as awareness across the UK veterinary profession has increased, imported dogs have been tested whilst clinically well, in part due to protocols put in place by some veterinary practices and companies for health and safety reasons.

Between 2020 and 2022, there were 100 epidemiologically distinct B. canis incidents reported to the APHA Brucella Reference Laboratory (9 in 2020, 36 in 2021, 55 in 2022). There were 262 dogs tested as part of these investigations, of which 143 tested positive (15). Many of these cases have been determined based on serology and epidemiological links, rather than through B. canis isolation by bacterial culture, which is not an appropriate frontline diagnostic test.

In the first quarter of 2023, there were 22 epidemiologically separate incidents reported to the APHA Brucella National Reference Laboratory where there was strong evidence of infection with B. canis (16). Investigations into these incidents resulted in the testing of 103 dogs in total, of which 43 were found to be serologically positive for B. canis. Many of these cases were again determined as positive based on serology and epidemiology, rather than definitively confirmed as infected by bacterial culture. Compared to the same period last year, the number of incidents in the first quarter for 2023 had increased more than 2-fold. This increase is most likely due to the greater awareness of the presence of B. canis within the UK.

Clinical signs of infection have varied between the 22 seropositive (index) dogs in the first quarter of 2023: 19 dogs had no clinical signs, one dog presented with discospondylitis, and 2 dogs presented with spinal pain. 21 of the incidents identified during the first 3 months of 2023 were associated with the importation of dogs into the UK. Most of these imported dogs originated from Romania (14), but they also came from Bosnia (1), Greece (1), Japan (1), Portugal (1), Russia (1), Serbia (1) and Spain (1).

The index case of the 22nd incident identified during this time period involved bacteriological isolation of B. canis from cultures of blood from a puppy (discospondylitis case). It was born at an unlicensed breeding premises in Wales. In the resulting investigation, and as of July 2023, 82 associated dogs have been tested and 22 were found to be serologically positive (including the index puppy), located at several different homes. In the second quarter of 2023, there have been a further 48 epidemiologically distinct incidents across the UK, again all associated with imported dogs and their contacts. This includes one additional incident involving dog breeding.

The imported cases identified to date have generally been diagnosed in dogs adopted by UK owners from organisations specialising in rehoming dogs from overseas. The vast majority are in young dogs imported from Romania. A previous review of domestic dog commercial import data by Defra found that to end of November 2020, commercial imports of dogs from Romania had increased in 2020 by 51% (29,348 dogs brought into the country by commercial means) compared to 2019 imports. The increasing numbers of commercial movements year on year also applies to several other countries, but numbers of dogs arriving from Romania per year remain a significant part of the total number of commercial movements per year (see Table 1).

In addition, it is important to note that in April 2022, England, Scotland and Wales introduced a safeguarding measure, which banned commercial movements of cats and dogs from Belarus, Poland, Romania and Ukraine in response to disease risks associated with the crisis in Ukraine. This was lifted on 29 October 2022 and replaced with a targeted safeguarding measure which allowed some commercial imports to resume from these countries, but subject to additional restrictions to protect biosecurity. This accounts for the large reduction in movements from Romania in 2022.

Table 1. Commercial and non-commercial dog movements into the UK between 2018 to 2022, by country of origin

Year of movement	2018	2019	2020	2021	2022
Commercial movements^*
Bosnia and Herzegovina	41	174	1,636	-	0
Bulgaria	216	220	222	1,093	2,273
Croatia	265	153	153	2,003	2,897
Cyprus	3,566	3,457	4,246	3,758	3,190
Greece	107	294	563	1,017	431
Hungary	1,585	2,145	5,065	4,517	2,593
Republic of Ireland	7,828	7,368	5,814	6,658	6,719
Poland	881	1,160	3,945	5,593	1,271
Romania	17,189	19,487	32,525	38,081	10,485
South Africa	279	529	519	1,522	771
Spain	4,995	4,891	6,475	5,909	4,845
USA	2,429	2,604	1,592	966	672
Total from above (EU only)	36,632	39,175	59,008	68,629	34,704
Total of commercial EU	37,144	39,566	60,188	72,766	37,284
Total of commercial (rest of world)	4,169	4,997	6,764	5,533	3,867
Total commercial	41,313	44,563	66,952	78,299	41,151
Non-commercial movements
Total of non-commercial movements (no country breakdown)	312,996	308,404	186,629	165,871	282,909
Total dog movements	354,309	352,967	253,581	244,170	324,060

*specific country of origin only listed if more than 1,000 dogs in at least one year

In Table 1, non-commercial movements relate to the movement of owned pets, both those originating in UK and those moving into UK from abroad. Historically this would be by use of a Pet Passport, but now UK pets cannot use a passport to travel but instead are issued with a health certificate for each journey. Movements by owned dogs are not risk free. Some of these dogs may be travelling internationally to be deliberately bred, but data on the number of movements that this may apply to are unavailable. In addition, there is some abuse of the non-commercial rules to bring in dogs for onward sale or for rehoming.

Are effective control measures in place to mitigate against these routes of introduction?

Outcome

No.

Quality of evidence

Satisfactory.

Infected dogs (and potentially germplasm) arriving in the UK from endemic countries present an ongoing exposure risk to the UK canine and human populations. However, a lack of or limited testing and/or reporting in other nations makes identifying a country as B. canis endemic problematic. There are no national requirements for B. canis safe sourcing or pre/post-import testing for B. canis from endemic counties. Some charities and rescue organisations are now routinely undertaking pre- or post-import testing. However, it is currently unknown what proportion of imported dogs from specific countries are infected. Imported B. canis infected dogs have been reported sporadically in the past. Some targeted testing of groups of rescue dogs carried out by APHA and the Dogs Trust detected prevalence rates of between 1 and 5% (17).

The reason(s) for the apparent sudden identification of a series of seropositive dogs in the UK since summer 2020 is currently not known. However, by 2021, awareness raising (and the legislative change to make B. canis a reportable disease in dogs) would have led to a greater level of diagnostic testing in potentially infected dogs suffering clinical disease. Since then, as veterinary knowledge on the risk of B. canis in imported dogs further increased, more samples have been submitted for B. canis testing from dogs with no clinical disease. Submissions for serological testing at APHA have increased from 1,001 submissions in 2020, to 5,773 submissions in the first half of 2023 (Table 2).

Table 2. The number of samples from dogs submitted for B. canis serological testing at APHA, by year

Year	Number of submissions
2018	1,332
2019	1,192
2020	1,001
2021	2,596
2022	4,662
2023 (January to June)	5,773

Do environmental conditions in the UK support the natural vectors or reservoirs of disease?

Outcome

Yes.

Quality of evidence

Good.

While not a true vector borne disease, the dog acts as a reservoir for zoonotic infection. There are believed to be 11 to 12 million dogs living in the UK. The vast majority will be living with owners in domestic households. 2023 data indicates that 31% of UK households have one or more dogs (18, 19).

Will there be human exposure?

Outcome

General UK population: No.

Higher risk groups (for example dog breeders, kennel, veterinary and laboratory staff and owners of infected dogs, especially those which are breeding or birthing): Yes.

Quality of evidence

Satisfactory.

B. canis has been isolated from canine seminal fluids, vaginal secretions, post-abortion and post-parturition vaginal fluids. Whilst B. canis has been isolated from urine and – to a lesser extent – canine saliva and nasal secretions, direct contact with contaminated tissues and fluids associated with parturition or spontaneous abortion in infected dogs is believed to present the greatest risk of exposure to human and other canine contacts. There may also be a risk of human exposure to B. canis through contact with joint fluid, blood and tissue from infected dogs (8, 20, 21).

Thus, individuals with the potential for exposure to B. canis infected dogs or B. canis contaminated materials either in an occupational or domestic setting (for example dog breeders, kennel, veterinary and laboratory staff and owners of infected dogs, especially those which are breeding or birthing) are regarded as those at greatest risk of exposure to infection. The risk of human infection in these settings is likely to be reduced if adequate PPE is worn. The risk from a neutered, infected dog cannot be ruled out, but is likely to be less than an unneutered dog with infection.

Transmission of Brucella species to laboratory workers is well described (22) and positive test results in staff exposed to B. canis isolates from human cases have been reported (23, 24). Risks to staff can be managed by following good practice guidelines (25).

As of July 2023, 2 laboratory-confirmed B. canis human infections have been identified in the UK. The first human case was detected following presentation at a hospital. This case had extremely close, direct contact with abortion material from an imported dog. The case was an immunocompromised individual and required hospitalisation for treatment. Following confirmation in the human, the dog was tested and was found to be positive, as were other dogs in the household which had also had contact with the abortion material.

The second case, who was asymptomatic and had no known co-morbidities, likely acquired infection from an infected dog that they monitored during anaesthesia and undertook post-operative care for in a veterinary practice setting. The dog was not known to be infected at the time but became ill at a later date and tested positive, after which the person was traced and tested.

In terms of risk from treated or managed infected dogs, owners and handlers should be made aware of the ongoing but reduced risk of infection and be advised of possible symptoms of B. canis infection in humans. Owners, particularly those with underlying conditions which put them at higher risk of severe infection, should inform their health professionals of possible exposure to B. canis.

Are humans highly susceptible?

Outcome

No.

Quality of evidence

Poor.

There are no large-scale studies that describe underlying risk factors in humans for becoming infected with B. canis following exposure. As a rare infection in humans, there are a limited number of case reports published in the scientific literature. Cases have been described in individuals across a range of ages, in individuals with no known medical conditions, and in people living with conditions, such as HIV, or taking treatments that compromise their immune system (23, 26, 27).

Although small outbreaks with 2 or more human cases have been described, many cases appear to be isolated and sporadic. Several studies have assessed or tested case contacts and found no additional cases (24, 28 to 30). It is not clear whether this is related to individual level risk factors, exposure, or other contributing variables.

Immunocompromised individuals and children (aged under 5 years) may be at greater risk of B. canis infection (8). For example, Dentinger and others described transmission of B. canis to a child from an infected puppy, resulting in febrile illness in the child. Four adults in the same household, all with exposure to the puppy, did not develop clinical signs (31).

There are several case reports of B. canis infections in individuals living with HIV that had exposure to B. canis infected dogs (26, 27, 32), highlighting the potential risk to this group.

It should be noted that there is a paucity of evidence determining specific risk factors that may result in increased susceptibility to B. canis infection.

Outcome of probability assessment

The probability of human infection with B. canis in the general UK population is considered Very Low.

The probability of infection for individuals with greater likelihood of exposure to B. canis infected dogs or contaminated materials (for example dog breeders, kennel, veterinary and laboratory staff and owners of infected dogs, especially those which are breeding or birthing) would be considered Low.

Question 4

Step 2: Assessment of the impact on human health

Poor.

The nonspecific nature of symptoms associated with B. canis infection in humans, coupled with a low index of suspicion by physicians, and the inability of standard serological tests for brucellosis to detect infection with B. canis, may result in under-ascertainment of human cases within the UK.

Yes.

Quality of evidence

Good.

There are effective antibiotic regimens for treating human brucellosis, though options are more limited for certain groups such as pregnant women (45). Most human cases of B. canis described in the published literature received treatment with antibiotics.

Relapse of infection has been described in B. canis (46).

Relapse and treatment failure are well described in human brucellosis cases more generally (47). Immunocompromised people may also be more difficult to treat due to drug interactions.

Outcome of impact assessment

The impact of Brucella canis from infected dogs on human health for the UK population is considered Very Low to Low.

Severe disease associated with B. canis infection has been reported, and immunocompromised individuals may be at higher risk of severe infection. There is, however, a lack of evidence to determine specific risk factors which contribute to disease severity and/or poorer clinical outcomes, as well as a paucity of evidence and understanding around the long-term impact of sequelae from infection.

Question 5

Annexe A: Assessment of the probability of infection in the UK population algorithm

Accepted Answer

Question 6

Accessible text version of Annexe A

Accepted Answer

Outcomes are specified with (Outcome) beside the appropriate answer.

Question 1: Is this a recognised human disease?

Yes

Go to question 3. (Outcome)

No

Go to question 2.

Question 2: Is this a zoonosis or is there a zoonotic potential?

Yes

Go to question 4.

No

The probability of infection in the UK population is considered very low.

Question 3: Is this disease endemic in humans within the UK?

Yes*

Go to question 5.

No

No

The probability of infection in the UK population is considered moderate.

Question 7

Annexe B: Assessment of the impact of infection in the UK population algorithm

Accepted Answer

Question 8

Go to question 10.

No

No

The impact of infection in the UK population is considered very high.

Question 9

References

Accepted Answer

Leclerq SO, Cloeckaert A and Zygmunt MS. Taxonomic Organization of the Family Brucellaceae Based on a Phylogenomic Approach. Frontiers in Microbiology. 2020; 10. DOI: 10.3389/fmicb.2019.03083
Spickler AR. Brucellosis: Brucella canis. The Center for Food Security and Public Health. Accessed 24 July 2023. 2018
Lucero N, Corazza R, Almuzara M and others. Human Brucella canis outbreak linked to infection in dogs. Epidemiology & Infection. 2010; 138: 280 to 285. DOI: 10.1017/S0950268809990525
Olivera M and Di-lorenzo C. Aislamiento de Brucella canis en un humano conviviente con caninos infectados. Informe de un caso. Colombia Medical. 2009; 40: 218 to 220
Krueger WS, Lucero NE, Brower A and others. Evidence for unapparent Brucella canis infections among adults with occupational exposure to dogs. Zoonoses and Public Health. 2014: 1 to 10. DOI: 10.1111/zph.12102
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About the Human Animal Infections and Risk Surveillance group

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Summary

Assessment of the risk of infection in the UK

Probability

Impact

Level of confidence in assessment of risk

Evidence gaps

Actions and recommendations

Step 1: Assessment of the probability of infection in the UK human population

Is this a recognised human disease?

Outcome

Quality of evidence

Background

Is the disease endemic in humans within the UK?

Outcome

Quality of evidence

Is the disease endemic in animals within the UK?

Outcome

Quality of evidence

Are there routes of introduction into animals in the UK?

Outcome

Quality of evidence

Table 1. Commercial and non-commercial dog movements into the UK between 2018 to 2022, by country of origin

Are effective control measures in place to mitigate against these routes of introduction?

Outcome

Quality of evidence

Table 2. The number of samples from dogs submitted for B. canis serological testing at APHA, by year

Do environmental conditions in the UK support the natural vectors or reservoirs of disease?

Outcome

Quality of evidence

Will there be human exposure?

Outcome

Quality of evidence

Are humans highly susceptible?

Outcome

Quality of evidence

Outcome of probability assessment

Step 2: Assessment of the impact on human health

Is there human-to-human spread of this pathogen?

Outcome

Quality of evidence

Is there zoonotic or vector borne spread of this pathogen?

Outcome

Quality of evidence

For zoonoses or vector-borne disease is the animal host or vector present in the UK?

Outcome

Quality of evidence

Is the UK human population susceptible?

Outcome

Quality of evidence

Does it cause severe disease in humans?

Outcome

Quality of evidence

Is it highly infectious to humans?

Outcome

Quality of evidence

Would a significant number of people be affected?

Outcome

Quality of evidence

Are effective interventions (preventative or therapeutic) available?

Outcome

Quality of evidence

Outcome of impact assessment

Annexe A: Assessment of the probability of infection in the UK population algorithm

Accessible text version of Annexe A

Question 1: Is this a recognised human disease?

Yes

No

Question 2: Is this a zoonosis or is there a zoonotic potential?

Yes

No

Question 3: Is this disease endemic in humans within the UK?

Yes*

No

Question 4: Is this disease endemic in animals in the UK?

Yes

No

Question 5: Are there routes of introduction into animals in the UK?