In 2013, Estonia was officially declared a rabies-free country
Many game-borne diseases also threaten domestic animals. The best known of these are rabies, African swine fever, avian influenza, echinococcosis, and scabies.
Rabies
Rabies is a viral disease that is incurable and always fatal. The incubation period of the disease can be from a few weeks to a few years, and the virus remains viable for two weeks after the death of the diseased animal. Rabies can infect all mammals (domestic and wild), but also humans. Rabies infection is the result of the bite of a diseased animal. Rabies damages the nervous system and most of the symptoms of the disease are related to a change in the animal’s behaviour: it starts behaving differently than usual – for example, a wild animal is no longer afraid of humans. A change in lifestyle is also characteristic; for example, an animal that moves around at night starts to move about during the day. Fear of water and an unsteady gait and paralysis in the final stages of the disease are also indicative of rabies.
Rabies was very common in Estonia during the last half a century and 200–300 cases of the disease were diagnosed in the laboratory every year. In the years 2005–2010, oral rabies vaccination of wild animals was carried out throughout Estonia, and thus, the disease receded rapidly. In 2013, Estonia was declared an officially rabies-free country, and by implementing anti-rabies measures (in particular the vaccination of wild animals in the buffer zone at the state border, compulsory annual vaccination of pets, and restrictions on the cross-border movement of pets), we have been able to maintain this situation. At the same time, the risk of a recurrence of rabies in Estonia is continuously high, as Russia has not eradicated the disease. The few recent cases of rabies have been linked to the movement of animals across national borders [1].
African swine fever
African swine fever is a highly contagious and acute viral disease of domestic pigs and wild boars. The disease is characterised by fever, bleeding, inflammatory changes in the organs, and high mortality (up to 100% of animals). Swine fever does not affect other animal species or humans, but they can transmit the virus.
The first case of the African swine fever in Estonia was diagnosed in 2014, and in the following year, the African swine fever was also found in domestic pigs [2].
Swine fever destroyed a large part of the Estonian wild boar population and caused great economic damage to Estonian pig farmers. The fever spread rapidly from the forest to the farms and led to farm closures and export restrictions. The number of domestic pigs decreased by about 15% due to the disease. In 2015–2016, Estonian pig farmers estimated their loss of income and additional costs related to biosafety at over 40 million euros [3].
Avian influenza
Avian influenza (type A H5N1) is a highly contagious and acute viral disease of birds. The disease is one of the most dangerous infectious animal diseases, causing mass infection in birds, high mortality, and extensive economic damage.
All poultry and game birds are susceptible to the avian influenza, but humans can also become infected. The source of infection is sick birds or birds that have survived the disease, but are still infectious. The infection of birds occurs through the gastrointestinal tract or respiratory tract. There is no treatment for sick birds and the disease is acute. In the event of an outbreak, a quarantine is established, and sick birds and birds suspected to be sick are killed and destroyed [4].
Scabies
Among wild animals, sarcoptosis, or scabies, is quite common. Some time ago, it was known mainly as a disease of foxes and raccoon dogs, but now, it has also spread to wolves and even lynxes. This parasitic disease is caused by Sarcoptes scabiei, an itch mite of about 0.2 mm and thus invisible to the naked eye.
The disease is spread through direct contact. As mites are very viable and can survive up to a week without a host, infection also occurs through surfaces contaminated with mites (burrows, beds, scratching spots, feeding dishes). The disease can also very easily be transmitted to dogs [5].
The itch mites damage the skin of a diseased animal by drilling passages into it, multiplying in large numbers, and feeding on lymph tissue. As a result of the mites’ life activity, a strong itching sensation occurs, which causes the animal to constantly scratch itself, causing an increase in skin damage and partial to complete hair loss. Although scabies only affects the surface of the skin and not directly any other organ system, not treating the animal (for example in wild animals) significantly reduces the animal’s competitiveness in the struggle for survival [6].
Humans can also become infected with canine or fox scabies, but because animal mites are unable to reproduce in human skin, they die within a week or two, and the person can be cured without treatment.
Scabies in wild animals cannot be prevented, because the treatment is specimen-based. However, a dog with scabies definitely needs treatment, and a veterinarian must be consulted for an accurate diagnosis and correct treatment. As scabies is a parasitic disease, the bed and doghouse of the dog also need thorough parasite control.
Echinococcosis
Echinococcosis is usually caused by Echinococcus granulosus (dog tapeworm) and Echinococcus multilocularis (a cyclophyllid tapeworm). The final hosts of E. granulosus in Estonia are wolves and dogs and the intermediate hosts are game ungulates, sheep, pigs, and cattle. The larvae are usually located in the liver and lung of the intermediate host. The final hosts of E. multilocularis are mainly foxes, raccoon dogs, and the intermediate hosts are small mammals, rodents (mice). Larvae are located in the liver of the intermediate host. Parasites can also accidentally enter humans and rodents, especially mice. The worm lives as a parasite in the various internal organs (e.g. liver, lung) of the intermediate host.
Unlike E. granulosus, larvae of E. multilocularis are able to reproduce in the intermediate host and spread through blood vessels to other organs.
The final host is not exhausted by the infection, but the intermediate hosts may die. Intermediate hosts become infected through food and water contaminated with the parasite’s eggs. People can also accidentally become the intermediate hosts of tapeworms. The eggs can end up in our hands and mouth when picking up and eating contaminated forest gifts or even when stroking an infected domestic animal.
E. granulosus is widespread around the world and E. multilocularis is widespread in the northern hemisphere. According to the Health Board, echinococcosis is so far a rare infectious disease in Estonia.
Last modified: 12.01.2022
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[1] https://pta.agri.ee/tarbijale-ja-eraisikule/lemmikloomad/marutaud
[2] https://www.agri.ee/taime-ja-loomatervis/sigade-aafrika-katk
[3] https://www.agri.ee/sites/default/files/content/uuringud/2016/uuring-2016-sak-sealihasektor.pdf
[4] https://pta.agri.ee/lindude-gripp-kuulub-eriti-ohtlike-loomataudide-hulka
[5] http://www.ejs.ee/karntobi-kahepalgeline-nakkushaigus/
[6] https://pta.agri.ee/tarbijale-ja-eraisikule/lemmikloomad/haigused-ja-vaktsineerimine#krntbi