Pigeon tick – an unexpected cause of allergic reactions

Pigeon tick (Argas reflexus) is a species-specific parasite of pigeons and, like its host, is mainly found in attics, lofts, church towers and pigeon houses. It is keen on urban pigeons, which are very abundant in large and densely populated cities [2]. However, it attacks other animals and humans sporadically when natural hosts are not available [1].

It is one of the largest and longest-lived ticks (about 10 years) and is extremely resistant to lack of food (it can survive 5 years without food) [1]. It is brown or flesh-coloured and is characterised by the fact that its mouthparts hide under the rest of its body. This means that when we look at this tick from above, only its legs are visible [1].

The pigeon tick spends the winter in a dormant state, from which it emerges in the first days of April. It is active mainly at night, and during the day it can hide, for example, in cracks in walls, under mouldings and wallpaper [1,3]. Night bites from this tick can even cause the death of the bird, especially if the parasite attacks a chick.

The list of pathogenic microorganisms transmitted by pigeon tick is very long. It includes tick-borne encephalitis virus, Grand Arbaud and Ponteves viruses or Salmonella enteritidis [1].

The pigeon tick drinks blood for half to one and a half hours, after which it falls off its host [4]. After its bite, a small haemorrhagic spot, usually not painful, first appears on the skin [1,3]. Then an itchy blister develops in the same area. Some people may experience persistent itching as a result of the bite [3]. The area around the blister is reddened and swollen. Sometimes there is enlargement of the local lymph nodes, which become painful [3]. These changes are usually felt for a few days, but may persist for weeks in particularly sensitive individuals [1].

Substances in the saliva of the ticks can also cause localised inflammation of the lymphatic vessels and a number of systemic symptoms, such as:

• unwellness
• dizziness,
• fever,
• shortness of breath,
• anxiety,
• tinnitus,
• visual disturbances,
• nausea and vomiting,
• abdominal pains,
• diarrhoea,
• restriction of joint mobility [1,3].

However, the most serious effect of a pigeon tick bite is anaphylactic shock, which can occur in people with hypersensitivity to allergens contained in the saliva of this tick (the main allergen is Arg r 1). There are even cases of fatal anaphylaxis [1]. One such case was reported in Poland (more precisely in Sosnowiec). Fifteen ticks were found in the flat of a man who died as a result of anaphylaxis [3]. Severe allergic reaction in a person stung by this arachnid was first described in Polish studies in the 1970s.

In a study conducted on a group of patients in Upper Silesia with symptoms of allergy to pigeon tick, it was shown that in 25% of these patients, the bite resulted in the development of generalised urticaria or an asthma attack. The remainder developed only a local allergic reaction [2].

Allergy to pigeon tick is detected by serological tests with the determination of allergen-specific IgE antibodies and by spot skin tests with extract [1,3].

Human pigeon tick bites most often occur after removal of a bird’s nest or removal of a dovecote – and this happens even years after these works have been carried out [1,2]. The risk mainly affects people living on the top floors of buildings and workers in attics [1]. The described cases of bites concern people living in flats adjacent to attics (or in attics converted into flats), which previously housed pigeons [3].

Getting rid of ticks is very difficult. These ticks tend to hide in crevices, spread rapidly, can stop breathing for several hours [2] and are highly resistant to chemicals [3]. If the nest is not removed properly, the starved ticks left in the area begin to look for a new host [2]. Therefore, pest control should be carried out by professionals [2]. In some cases, it may even be necessary to scrape the plaster from the walls [2]. In order to prevent the ticks from entering the dwelling, all openings in the walls and around the windows should be blocked (temporarily this can be done with adhesive tape) [2].

It is also important to bear in mind the legal regulations involved. The urban pigeon is a legally protected bird. Therefore, a pigeon nest on a balcony can only be removed when it is empty [4]. To avoid the problem, it is therefore best to be foresighted and, before the peak of the nesting season begins, install a special safety net on the balcony [4].

It is also important to wash your hands thoroughly with soap after every contact with pigeons. These birds can carry not only pigeon ticks, but also 60 different pathogenic microorganisms [2].

Aleksandra Lipiec 

__________________

translation: Julia Majsiak

Publication: 12.04.2024
Updated: 18.03.2025