Lyme disease is increasingly common in Europe, with recent research finding it to be an emerging infectious disease in Scotland, regions of Italy, and also in Poland. The increase in numbers of cases of Lyme disease in Poland is largely focused on endemic areas such as Szczecin city and in the north-west of the country. Recent research published in the journal of Experimental and Applied Acarology details the presence of a range of bacteria in ticks taken from host animals in the Polish countryside and in forest parks.
Ticks (which, like mites, are members of the Acaridae family) tend to use animals such as roe deer, red deer, and wild boar as hosts in Poland. The Ixodes ricinus tick has three lifestages and requires a blood meal at each stage in order to progress to the next stage of development. These lifestages are larvae, nymph and adult, with the adult ticks typically laying their eggs on a host, allowing for the hatching larvae to get an immediate blood meal.
How Lyme Disease Spreads
Zoonoses like Lyme disease spread because animals carry the bacteria in their blood, thereby passing the bacteria onto ticks which then feed on and infect other animals at subsequent lifestages. A tick that feeds on an infected animal and then later bites a human can transmit Borrelial bacteria and cause Lyme disease. As such, efforts to understand the presence of bacteria in host animals can help with the creation of public health policy to raise awareness of and prevention efforts for Lyme disease.
Animals with Lyme Disease in Poland
In this latest research, Polish scientists looked at 880 questing nymphal ticks, i.e. ticks in the second stage of their life who were looking for a blood meal. They collected these ticks in forest parks of Szczecin city and rural forests in northwestern Poland, areas where Lyme disease is endemic. The researchers discovered that Ixodes ricinus larvae not only feed on small or medium animals, like mice, lizards, and birds, but also on deer and wild boar. In fact, these larger animals were the most prevalent hosts for these tick larvae.
The main reservoir for Lyme disease and additional zoonoses suc as Rickettsia in Poland appeared to be the European roe deer (Capreolus capreolus), and wild borad (Sus scrofa). The roe deer were infected with two species of Rickettsia and two species of Borrelia, and the boar carried one Rickettsia and three Borrelia species. The most common bacteria was Rickettsia helvetica, and the researchers also found several members of the B. burgdorferi sensu lato group and Borrelia miyamotoi bacteria that cause relapsing fever.
Borrelia garinii has long been considered the Lyme disease bacteria genospecies associated with birds and this research confirmed that association, although the authors noted that this appeared to be less common in natural habitats than previous research has indicated.
Why Lyme Disease Research is Necessary
Understanding which animals act as significant host reservoirs for zoonoses like Lyme disease and Rickettsia, and the type of bacteria carried by these animals and by a resident tick population, helps in the early identification of symptoms of infection and in environmental planning efforts to reduce human exposure to wildlife in endemic areas. This kind of research on Lyme disease in Poland can also be helpful for nearby countries as migratory animals will often carry ticks infected with pathogens.
Wodecka B, Rymaszewska A, Skotarczak B. Host and pathogen DNA identification in blood meals of nymphal Ixodes ricinus ticks from forest parks and rural forests of Poland. Exp Appl Acarol. 2014 Apr;62(4):543-55.