Diseases in nature

There are many different diseases which affect non-human animals, and the harm they cause is just as diverse. As we all know, diseases can be very painful. In fact, we often fail to realise that it may be possible to vaccinate or treat animals that are slowly killed by disease and avoid the harm caused to them. This is explained in our page Vaccinating and healing sick and injured animals.

Diseases can also disrupt the lives of animals. Not only do diseases cause animals to suffer, and in some cases eventually die, they can also significantly impair their capacity to survive. This can include them being unable to properly feed themselves or to find appropriate shelter when they need it. In turn, this can worsen the effects of the environmental conditions that animals suffer in and indirectly lead to more death.1

As it is difficult to notice when an animal is sick, there is a tendency to underestimate the harm that animals in the wild suffer due to disease. This is the case in a wide range of harms they suffer, but occurs especially in the case of disease. Better known diseases that affect animals in the wild are those that can be transmitted either to humans or to domesticated animals.2 But there are also many diseases affecting other animals, such as those in the wild.

Some diseases have symptoms that can be recognised visually. However, throughout natural history many animals have been selected to avoid showing any sign of pain or distress as those who did were targeted by predators. Therefore realising that an animal is sick is often difficult. This means that an animal may be suffering a great deal due to a condition that we are unable to recognise. In fact many diseases can’t be diagnosed unless one performs medical checks on the sick animal.

However, as more studies are carried out on how animals are affected by disease in the wild, our knowledge of this area is starting to change.3 More and more diseases affecting animals in the wild are now recognised and diagnosed.

There are so many diseases that affect non-human animals in nature that they cannot all be listed here. However, the following resources list some examples:

Animal disease information – The Center for Food Security & Public Health

A-Z list of significant animal pests and diseases – Queensland Government

Animal disease information – United States Department of Agriculture

Animal diseases – World Organisation for Animal Health4

Some diseases are hereditary, whilst others are a result of infections by viruses, bacteria or prions which are commonly transmitted through contagion, for example, by parasites.5

It is a common belief that it is perfectly natural for animals in the wild to suffer from disease and therefore there is nothing wrong with it. The idea of helping non-human animals in the wild is something many people have never considered. It may even seem immoral or absurd at first to do so. Here are two main reasons for such objections:

One is that it would be immoral to heal or vaccinate animals in nature. These concerns are addressed in Can animals in the wild be harmed the same ways as domesticated animals and humans?

Second is the claim that it is not possible to improve the health of animals living in the wild. The thought of curing animals or vaccinating them from the disease so they do not suffer may seem completely unrealistic. But is it really?

The answer, quite simply, is no. Healing or vaccinating wild animals are just two examples of how we can clearly help wild animals. This is an empirical fact and is explained in Vaccinating and healing sick and injured animals.

Disease, which is a source of great suffering and death, should not just be combatted when it affects humans, or when it affects non-human animals in ways that are also bad for humans. Disease should also be combatted when non-human animals are affected for their own sake, not simply due to human interests.

Further readings

Bengis, R. G.; Kock, R. A. & Fischer, J. (2002) “Infectious animal diseases: The wildlife/livestock interface”, Revue Scientifique et Technique, 21, pp. 53-65 [accessed on 28 November 2016].

Bosch, J.; Sanchez-Tomé, E.; Fernández-Loras, A.; Oliver, J. A.; Fisher, M. C. & Garner, T. W. (2015) “Successful elimination of a lethal wildlife infectious disease in nature”, Biology Letters, 11 (11) [accessed on 27 November 2016].

Curtis, C. F.; Brookes, G. D.; Grover, K. K.; Krishnamurthy, B. S.; Laven, H.; Rajagopalan, P. K.; Sharma, L. S.; Sharma, V. P.; Singh, D.; Singh, K. R. P.; Yasuno, M.; Ansari, M. A.; Adak, T.; Agarwal, H. V.; Batra, C. P.; Chandrahas, R. K.; Malhotra, P. R.; Menon, P. K. B.; Das, S.; Razdan, R. K.; & Vaidanyanathan, V. (1982) “A field trial on genetic control of Culex p. fatigans by release of the integrated strain IS-31B”, Entomologia Experimentalis et Applicata, 31, pp. 181-190.

Dame, D. A.; Woodward, D. B.; Ford, H. R. & Weidhaas, D. E. (1964) “Field behavior of sexually sterile Anopheles quadrimaculatus males”, Mosquito News, 24, pp. 6-16.

Daszak, P.; Cunningham, A. A. & Hyatt, A. D. (2000) “Emerging infectious diseases of wildlife – threats to biodiversity and human health”, Science, 287, pp. 443-449.

Delahay, R. J.; Smith, G. C. & Hutchings, M. R. (2009) Management of disease in wild mammals, Dordrecht: Springer.

Dobson, A. & Foufopoulos, J. (2001) “Emerging infectious pathogens of wildlife”, Philosophical Transactions of the Royal Society of London B: Biological Sciences, 356, pp. 1001-1012.

Gortázar, C.; Delahay, R. J.; Mcdonald, R. A.; Boadella, M.; Wilson, G. J.; Gavier-Widen, D. & Acevedo, P. (2012) “The status of tuberculosis in European wild mammals”, Mammal Review, 42, pp. 193-206.

Gortázar, C.; Díez-Delgado, I.; Barasona, J. A.; Vicente, J.; de la Fuente, J. & Boadella, M. (2015) “The wild side of disease control at the wildlife-livestock-human interface: A review”, Frontiers in Veterinary Science, 1, A. 27, pp. 1-27.

Han, B. A.; Park, A. W.; Jolles, A. E. & Altizer, S. (2015) “Infectious disease transmission and behavioural allometry in wild mammals”, Journal of Animal Ecology, 84 (3), pp. 637-646.

Harris, R. N. (1989) “Nonlethal injury to organisms as a mechanism of population regulation”, The American Naturalist, 134, pp. 835-847.

Hawley, D. M. & Altizer, S. M. (2011) “Disease ecology meets ecological immunology: Understanding the links between organismal immunity and infection dynamics in natural populations”, Functional Ecology, 25, pp. 48-60 [accessed on 5 November 2016].

Holmes, J. C. (1995) “Population regulation: a dynamic complex of interactions”, Wildlife Research, 22, pp. 11-19.

Hudson, P. J.; Rizzoli, A.; Grenfell, B.; Heersterbeek, H. & Dobson, A. (eds.) (2002) The ecology of wildlife diseases, Oxford: Oxford University Press, pp. 1-5.

Knipling, E. F. (1979) The basic principles of insect population and suppression and management. USDA handbook, Washington, D. C.: U.S. Department of Agriculture.

Newton, I. (1998) Population limitations in birds, San Diego: Academic Press.

Ng, Y.-K. (1995) “Towards welfare biology: Evolutionary economics of animal consciousness and suffering”, Biology and Philosophy, 10, pp. 255-285.

O’Dea, M. A.; Jackson, B.; Jackson, C.; Xavier, P. & Warren, K. (2016) “Discovery and partial genomic characterisation of a novel nidovirus associated with respiratory disease in wild shingleback lizards (Tiliqua rugosa)”, PLOS ONE, 11 (11) [accessed on 28 November 2016].

Simpson, V. R. (2002) “Wild animals as reservoirs of infectious diseases in the UK”, The Veterinary Journal, 163, pp. 128-146.

Tompkins, D. M.; Dunn, A. M.; Smith, M. J. & Telfer, S. (2011) “Wildlife diseases: From individuals to ecosystems”, Journal of Animal Ecology, 80, pp. 19-38.

Wildlife Data Integration Network (2013) “Wildlife disease: Index”, wdin.org [accessed on 23 March 2013].

Williams, E. S. & Barker, I. K. (eds.) (2008) Infectious diseases of wild mammals, New York: John Wiley and Sons.

Wobeser, G. A. (2005) Essentials of disease in wild animals, New York: John Wiley and Sons.

Wobeser, G. A. (2012) Diseases of wild waterfowl, Dordrecht: Springer.

Wobeser, G. A. (2013) Investigation and management of disease in wild animals, Dordrecht: Springer.


1 Beldomenico, P. M.; Telfer, S.; Gebert, S.; Lukomski, L.; Bennett, M. & Begon, M. (2008) “Poor condition and infection: A vicious circle in natural populations”, Proceedings of the Royal Society of London B: Biological Sciences, 275, pp. 1753-1759 [accessed on 8 April 2018].

2 Simpson, V. R. (2002) “Wild animals as reservoirs of infectious diseases in the UK”, op. cit. Gortázar, C.; Ferroglio, E.; Höfle, U.; Frölich, K.; Vicente, J. (2007) “Diseases shared between wildlife and livestock: A European perspective”, European Journal of Wildlife Research, 53, pp. 241-256. Martin, C.; Pastoret, P. P.; Brochier, B.; Humblet, M. F. & Saegerman, C. (2011) “A survey of the transmission of infectious diseases/infections between wild and domestic ungulates in Europe”, Veterinary research, 42, p. 70.

3 Barlow, N. D. (1995) “Critical evaluation of wildlife disease models”, in Grenfell, B. T. & Dobson, A. P. (eds.) Ecology of infectious diseases in natural populations, Cambridge: Cambridge University Press, pp. 230-259. Branscum, A. J.; Gardner, I. A. & Johnson, W. O. (2004) “Bayesian modeling of animal- and herd-level prevalences”, Preventive Veterinary Medicine, 66, pp. 101-112. Nusser, S. M.; Clark, W. R.; Otis, D. L. & Huang, L. (2008) “Sampling considerations for disease surveillance in wildlife populations”, Journal of Wildlife Management, 72, pp. 52-60. McClintock, B. T.; Nichols, J. D.; Bailey, L. L.; MacKenzie, D. I.; Kendall, W. & Franklin, A. B. (2010) “Seeking a second opinion: Uncertainty in disease ecology”, Ecology letters, 13 (6), pp. 659-674. Camacho, M.; Hernández, J. M.; Lima-Barbero, J. F. & Höfle, U. (2016) “Use of wildlife rehabilitation centres in pathogen surveillance: A case study in white storks (Ciconia ciconia)”, Preventive Veterinary Medicine, 130, pp. 106-111.

4 See The Center for Food Security & Public Health (2016 [2004]) Animal disease information, op. cit.; Queensland Government. Department of Agriculture and Fisheries (2018 [2010]) “A-Z list of significant animal pests and diseases”, op. cit.; Animal and Plant Health Inspection Service – United States Department of Agriculture (2015) “Animal disease information”, op. cit. See also Wikipedia (2013) “Category: Animal diseases”, Wikipedia [accessed on 29 August 2016].

5 Cole, R. A. & Friend, M. (1999) Field manual of wildlife diseases: Parasites and parisitic diseases, Lincoln: University of Nebraska [accessed on 16 April 2014]; Dantas-Torres, F.; Chomel, B. B. & Otranto, D. (2012) “Ticks and tick-borne diseases: A One Health perspective”, Trends in Parasitology, 28, pp. 437-446.

Animal Ethics in other languages