Is The Next Zoonosis Lurking In Your Back Yard?

 

I just had a recent adventure with rabbits.  Like the experience of many suburbanites, rabbits like to eat all our ornamental vegetation. My wife oversees that department, and she does not like to see that vegetation depleted. She has tried all the repellants and the rabbits keep coming.  She has talked about shooting them like her father used to, but I convinced her that was not a good idea.  She settled on the idea of live trapping the animals and releasing them in an area far away from the house – like a park or wildlife reserve.

I researched the legality of it all.  I was surprised to find out that rabbits are considered a nuisance animal in the state of Minnesota.  As such you can kill them by various means other than poisoning without a license and at any time. There are obstacles to both relocating rabbits or how to dispose of them. I contacted both the county and city natural resource departments. They told me it was illegal to relocate rabbits onto city, county, or state lands including parks and wildlife areas.  The officials confirmed that I did not need a hunting license to kill them, but that if I did kill a rabbit, I needed to report it to the DNR.  I did not let anyone know I thought that killing a rabbit was bad karma and I had no intention of killing them.

I was advised that if I did kill a rabbit, I needed to handle it with nitrile gloves and double bag it in plastic.  Even then I must contact my garbage hauler to make sure that I could dispose of it in the trash. There were no further instructions from officials on the next step if the garbage hauler refuses to take it – but based on how the conversations were going I thought it was probably digging a deep hole in the yard.

Minnesota is populated by one true rabbit species – the Eastern Cottontail (Sylvilagus floridanus) and two hare species – the Snowshoe Hare (Lepus americanus) and the White-tailed Jack Rabbit (Lepus townsendii).  The hares are probably more common in the north.  The defining characteristics of rabbits versus hares include fewer chromosomes (44 versus 48), altricial birth state versus precocial, shorter gestation (30-31 days versus 42 days), smaller bodies and shorter ears, highly social versus solitary, and softer food preference (grass and leafy vegetables opposed to bark, twigs, and buds).  An altricial birth state means offspring are born in a state where they are unable to feed or regulate body temperature and as a result need a prolonged period of close parenting. In the past 10 years there have also been cladistic analyses based on nuclear and mitochondrial DNA.  Like all taxonomy there is some mismatch of classification.  Jackrabbits are hares and Rock hares are rabbits.     

Even before I heard those biosecurity measures from public officials, I researched the issue of rabbit to human disease transmission (1).  Domestic pet rabbits were noted to spread the expected pathogens like E. coli, Salmonella spp, Yersinia pseudotuberculosis, and Cryptosporidium.  They can also be a source of Hepatitis E.   Pasteurella multocida and Bordetella bronchiseptica can be spread as respiratory infections in humans.  Rabies was detected in one group of rabbits thought to have been infected by a wild animal.  Dermatophytes and rabbit fur mites can cause localized infections in humans.

Wild rabbits harbor Francisella tularensis the infectious bacteria causing tularemia. Tularemia is a systemic multisystem disease that can be difficult to diagnose and treat. In the worst case it can cause shock and death.  It has also been implicated as an agent that could be used for bioterrorism.   Rabbits can also have Babesia spp and Anaplasma phagocytophilum the infectious agents that cause babesiosis and human granulocytic anaplasmosis.  

Babesiosis is caused by the obligate intraerythrocytic protozoan parasite Babesia microti (2).  Severity of the illness is related to degree of parasitemia (concentration of parasites in the bloodstream) and host factors that lead to compromised immune response including age. In the extreme cases it can lead to life threatening complications that require acute care like acute renal failure, disseminated intravascular coagulation (DIC), congestive heart failure, acute respiratory distress syndrome (ARDS), and others.

Human granulocytic anaplasmosis is caused by intracellular bacteria from the Anaplasmataceae family – in this case Anaplasma phagocytophilum (3).  It is a tick-borne disease meaning that the major reservoir for the agent is small mammals who transmit it to humans via a tick vector.  Most people who are infected present with an acute flu-like illness that can progress to involved multiple systems (rash, pneumonitis, myocarditis, meningoencephalitis, secondary infections, coma).

Most of the infections identified from rabbits come from direct contact, contact with infected surfaces, and contact with blood, feces, or other bodily fluids. People raising rabbits as pets, as a food source, or hunters would appear to be at highest risk and the suggested biosecurity measures would be protective.  In talking with the local wildlife officials their concern was that rabbit relocation could be a significant source of disease spread – specifically Rabbit Hemorrhagic Fever – a viral illness that results in most rabbits dying of hepatic necrosis 48-72 hours post infection. 

Rabbit Hemorrhagic Disease Virus (RHDV) was first described in China in 1984 and has spread worldwide (4).  It is a small non-enveloped RNA virus about 40 nm in diameter.  The genome is about 8 kilodaltons is size. It is taxonomically classified in the Calciviridae family.  That family has 11 genera (Norovirus, Nebovirus, Sapovirus, Lagovirus, Vesivirus, Nacovirus, Bavovirus, Recovirus, Salovirus, Minovirus, and Valovirus). (Smertina) (5).  Of the major genera Norovirus and Sapovirus cause acute gastroenteritis in humans.  The etiological agent can only be distinguished by laboratory testing. The Lagovirus genus also includes European brown hare syndrome virus (EBHSV) (6).  While the original RHDV virus was species specific – there is a newer strain (RHDV2 (GI.2) that infects both rabbits and hares and is lethal to both.

All these details build a compelling story far beyond suburban landscapers wanting to protect their plants.  The recent pandemic and likely crossover of a bat coronavirus into the human population as well as past crossovers like human immunodeficiency virus and avian influenza highlight the dangers of proximity to animals with high levels of infection. There have been two recent worldwide epidemics of rabbit hemorrhagic disease virus (RHDV) initially from 1984 to the 1990s and more recently from 2010 to present.  At no point in my medical career was I made aware of this viral spread despite hearing about viral spread in other species like elk wasting disease. Evolutionary biologists have suggested the RHDV virus has been in existence for 150 years (7-10). 

The pathogenesis of the virus is known at this point. It causes apoptosis of hepatic cells and hepatic necrosis.  One of the main protective mechanisms’ antioxidant suppression of oxidative stress is overwhelmed.  Apoptosis of endothelial cells leads to procoagulant activity and disseminated intravascular coagulopathy (DIC) and resulting hemorrhage and shock. RHDV2 has enhanced virulence factors and previous infection with RHDV does not confer immunity.     

The risk of RHDV crossover to human is estimated to be low based on several factors.  First, in a large study of human exposure of 269 people exposed to infected rabbits there were no episodes of disease or antibody formation to the virus in any of those people.  Second, there is continued host specificity to lagomorphs with limited documented crossovers to other species (Alpine musk deer, Eurasian badgers).  Third, there is limited ability for viral replication in other mammalian models including mice with immune deficits (interferon 1 receptor deficits). Fourth, high specificity for histo-blood group antigens (HBGAs) (11-12) – that is the virus binds to rabbits specific HBGAs and cell receptor specificities.  Fifth, the molecular biology of the rabbit versus human HBGAs are such that there are no functional binding sites for RHDV virus.

In my efforts to understand why rabbits are considered a nuisance animal and a biohazard, I uncovered an interesting set of factors. Given the rabbit exclusive pandemics that have occurred I can understand why wildlife officials are concerned about the spread of disease from transported rabbits.  The concern about disease transfer to humans from feces, saliva, other bodily fluids, and rabbits carcasses also makes sense. One of my colleagues pointed out that there is a tularemia vaccination for dogs.  Other rabbit predators may be as susceptible as humans to many of these diseases and they are probably relatively protected from RHDV because of the aforementioned factors.  This post also highlights the need for veterinary virologists and epidemiologists to track the evolution and crossover potential of these viruses.   That used to happen in an organized way for Influenza viruses through the World Health Organization (WHO) but the current anti-science and anti-medicine administration has pulled the US out of that organization and had probably negatively impacted the viral surveillance necessary to prevent zoonoses.

At the practical level, if you are a suburbanite interested in protecting your hastes from rabbits, barriers like wire cages are recommended by the public officials I talked with.  Be sure to check with them about live trapping and relocation or other means of controlling rabbits. The literature I reviewed on live trapping recommended always using gloves when handling the trap to avoid contaminants and prevent the transfer of human scent to the trap.  Rabbit waste and carcasses should also be avoided by homeowners and pets.  Some of the pathogens in the table are transmitted by ticks – so the same precautions to prevent Lyme Disease apply.   In terms of surveillance, your state department of natural resources is probably the best resource.   They directed me to the problem of RHDV that is not listed in the human literature but is an ongoing global problem for rabbits at the epizootic level.

The lesson from rabbits so far is that non-humans also have epidemics or epizootics. The only epizootics that humans seem to pay attention to affect domesticated animals or potential high risk crossover situations like avian influenza. Those contacts of humans and animals in suburbia bear watching both for the immediate threats and implications for handling biological materials – but also the potential long term consequences. (13-16).    

 

George Dawson, MD, DFAPA

Supplementary 1:  I thought this was an excellent graphic but could not figure out where to put it in the above essay. It is an estimate of worldwide mortality due to infectious diseases. Zoonotic origins are on the left of the diagram and non-zoonotic on the right.  The authors point out that boundary is not as clear cut as it seems since common causes of crossover like bats, rats, and mice occupy the same biosphere.  In the case of rabbits I would say the backyard is the same biosphere.  

60% of human diseases have animal origins.  Based on the lab origins rhetoric of the past few years Mother Nature is by far the most significant bioterrorist.  It also speaks to why any reasonable approach to prevent these outbreaks requires infectious disease and epidemiology expertise in both human and veterinary medicine.

The graph also contains the implicit information on the non-zoonotic side.  The increasing candida auris infections are thought to be due to man-made climate change.  Warm blooded animals were thought to have natural resistance to fungal infections based on higher body temperature where fungi could not survive. That evolutionary advantage is vanishing due to increasing ambient temperatures and fungal adaptation.  There are also 5 vaccine preventable diseases. There is an active anti-vaccination campaign that has reduced access to some of these vaccinations.         

Graphic is reproduced here via Copyright: © 2022 Weiss RA et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, CC BY 4.0 which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.  Original work is cited as reference 14.

References:

1:  Cotton CN.  Zoonoses: Animals other than dogs and cats.  UpToDate.  Accessed March 31, 2026.  https://www.uptodate.com/contents/zoonoses-animals-other-than-dogs-and-cats

2:  Krause PJ.  Babesiosis: Clinical manifestations and diagnosis.  UpToDate.  Accessed March 31, 2026.  https://www.uptodate.com/contents/babesiosis-clinical-manifestations-and-diagnosis

 3:  Dumler JS.  Biology of Anaplasmataceae.  UpToDate.  Accessed March 31, 2026.  https://www.uptodate.com/contents/biology-of-anaplasmataceae

4:  Abrantes J, van der Loo W, Le Pendu J, Esteves PJ. Rabbit haemorrhagic disease (RHD) and rabbit haemorrhagic disease virus (RHDV): a review. Vet Res. 2012 Feb 10;43(1):12. doi: 10.1186/1297-9716-43-12. PMID: 22325049; PMCID: PMC3331820.

5:  Smertina E, Hall RN, Urakova N, Strive T, Frese M. Calicivirus Non-structural Proteins: Potential Functions in Replication and Host Cell Manipulation. Front Microbiol. 2021 Jul 14;12:712710. doi: 10.3389/fmicb.2021.712710. PMID: 34335548; PMCID: PMC8318036.

6:  Fitzner A, Niedbalski W, Kęsy A, Rataj B, Flis M. European Brown Hare Syndrome in Poland: Current Epidemiological Situation. Viruses. 2022 Oct 31;14(11):2423. doi: 10.3390/v14112423. PMID: 36366520; PMCID: PMC9698305.

EBHSV can infect Sylvilagus spp but not European rabbits Oryctolagus cuniculus. 

7:  Fitzner A, Niedbalski W, Hukowska-Szematowicz B. Simultaneous Occurrence of Field Epidemics of Rabbit Hemorrhagic Disease (RHD) in Poland Due to the Co-8:  8: 

8:  Presence of Lagovirus europaeus GI.1 (RHDV)/GI.1a (RHDVa) and GI.2 (RHDV2) Genotypes. Viruses. 2025 Sep 26;17(10):1305. doi: 10.3390/v17101305. PMID: 41157577; PMCID: PMC12568209.

9:  Abrantes J, van der Loo W, Le Pendu J, Esteves PJ. Rabbit haemorrhagic disease (RHD) and rabbit haemorrhagic disease virus (RHDV): a review. Vet Res. 2012 Feb 10;43(1):12. doi: 10.1186/1297-9716-43-12. PMID: 22325049; PMCID: PMC3331820.

10:  Kerr PJ, Kitchen A, Holmes EC. Origin and phylodynamics of rabbit hemorrhagic disease virus. J Virol. 2009 Dec;83(23):12129-38. doi: 10.1128/JVI.01523-09. Epub 2009 Sep 16. PMID: 19759153; PMCID: PMC2786765.

11:  Stowell CP, Stowell SR. Biologic roles of the ABH and Lewis histo-blood group antigens Part I: infection and immunity. Vox Sang. 2019 Jul;114(5):426-442. doi: 10.1111/vox.12787. Epub 2019 May 9. PMID: 31070258.

12:  Stowell SR, Stowell CP. Biologic roles of the ABH and Lewis histo-blood group antigens part II: thrombosis, cardiovascular disease and metabolism. Vox Sang. 2019 Aug;114(6):535-552. doi: 10.1111/vox.12786. Epub 2019 May 14. PMID: 31090093.

13:  Carman JA, Garner MG, Catton MG, Thomas S, Westbury HA, Cannon RM, Collins BJ, Tribe IG. Viral haemorrhagic disease of rabbits and human health. Epidemiol Infect. 1998 Oct;121(2):409-18. doi: 10.1017/s0950268898001356. PMID: 9825794; PMCID: PMC2809540.

14:  Weiss RA, Sankaran N. Emergence of epidemic diseases: zoonoses and other origins. Fac Rev. 2022 Jan 18;11:2. doi: 10.12703/r/11-2. PMID: 35156099; PMCID: PMC8808746. (open access)

15:  Galindo-González J. Avoiding novel, unwanted interactions among species to decrease risk of zoonoses. Conserv Biol. 2024 Jun;38(3):e14232. doi: 10.1111/cobi.14232. Epub 2024 Jan 3. PMID: 38111356.

16:  Bengis RG, Leighton FA, Fischer JR, Artois M, Mörner T, Tate CM. The role of wildlife in emerging and re-emerging zoonoses. Rev Sci Tech. 2004 Aug;23(2):497-511. PMID: 15702716.