Ticks

Overview

Distribution in Italy and Europe

Ticks are common throughout the world and about 900 species are known to exist. Two families of ticks are present in Europe: the Ixodidae, also known as hard ticks because of the hard shield on their back, and the Argasidae, or soft ticks, which lack such shield. A total of 36 species, belonging to 7 genera, are currently found in Italy: the hard ticks are grouped into five genera (Ixodes, Rhipicephalus, Hyalomma, Haemaphysalis, Dermacentor), and the soft ticks into two (Argas and Ornithodoros). Ticks from the Argas and Ornithodoros genera usually feed on birds, and the species most commonly found in Italy is Argas reflexus, also known as “pigeon tick”. In Italy and Europe, the most common and important species from a medical perspective are: Ixodes ricinus (wood tick), Rhipicephalus sanguineus (brown dog tick), Hyalomma marginatum and Dermacentor reticulatus.

Life cycle

Ticks may feed on the same host or two or three different hosts during their life cycle, which consists of 4 stages: egg, larva, nymph and adult. After the eggs hatch, both females and males require a blood meal at every stage of their life cycle. Adult females also require a blood meal for egg production.

Ticks are usually not very selective of their hosts, which can include different animal species like dogs, deer, squirrels and even humans. Tick species that feed on large mammals may also parasitize birds while in their larva and nymph stages. The blood meal, during which ticks remain attached to their host, can be completed within hours (soft ticks), or within days/weeks (hard ticks).

Tick activity is strongly affected by temperature and humidity and, despite some exceptions, is concentrated in the warmer months. This is because, during the winter season, ticks tend to hide under rocks or burrow into the soil to find shelter from the cold. Soft ticks may hibernate over the winter months in rock crevices and cracks in the walls of hen houses and animal sheds. As temperatures rise, tick activity resumes and continues until the following autumn. Ongoing climate change, however, may affect tick activity in different ways depending on location.

Preferred habitats are usually areas of dense grass and shrub vegetation, but may vary depending on the tick species. The wood tick thrives in cool and wet climates, while the brown dog tick favours warm and dry environments or areas with sparser vegetation. The presence of ticks largely depends on the presence of potential hosts. This is why they are often found in stables, animal sheds and pastures.

Ticks do not jump or fly onto their host. They usually crawl up to the edge of vegetation and attach themselves to animals (including humans) as they brush past. Ticks are alerted to the presence of a potential host by its body heat and the carbon dioxide it exhales. After sinking its rostrum into the host’s skin, the tick starts sucking its blood: the bite is generally painless because the tick secretes small amounts of saliva with anaesthetic properties. The tick remains attached to its host for 2-7 days before dropping off.

Tick-borne diseases

Ixodid ticks can transmit pathogens to humans and cause a range of diseases, including: Lyme borreliosis, ehrlichiosis, rickettsial spotted fevers, tularemia, Q fever, babesiosis, viral encephalitis and Crimean-Congo haemorrhagic fever (mainly caused by species of the Hyalomma genus). Argasid ticks are a vector for diseases of lower epidemiological importance, such as tick-borne relapsing fever and Q fever. As temperatures get warmer, ticks come out of dormancy and start searching for a host. Therefore, most tick bites occur during spring and summer. Tick bites themselves are harmless to humans, but can transmit infections that may pose a health risk.

Several microorganisms are involved in the aetiology of these vector-borne diseases, including protozoa, bacteria and viruses. In Italy, the major tick-borne infectious diseases of epidemiological significance include:

• Tick-borne encephalitis (TBE) (mainly transmitted by the wood tick)
• Lyme disease (mainly transmitted by the wood tick)
• Rickettsiosis (mainly transmitted by the brown dog tick)
• Tick-borne relapsing fever
• Tularemia
• Tick-borne meningoencephalitis
• Ehrlichiosis.

Most of these diseases can only be diagnosed clinically, but prompt treatment with antibiotics in the early stages is usually successful, especially when bacteria are the aetiological agents. Only rarely (up to 5% of all cases) and in elderly people or children, can these infections be life-threatening.

Prevention

Some precautions can be taken to significantly reduce the risk of coming into contact with ticks, or at least to rapidly detect them before any disease is transmitted, such as:

• Wearing light-coloured clothes (to make it easier to spot a tick) that cover your extremities, long trousers tucked into light-coloured socks (or better still, boots) and preferably a hat
• Avoiding areas with tall grass and walking in the centre of trails to avoid contact with overgrown vegetation
• Carefully inspecting your body and clothing after hiking, and removing any tick you may find. Ticks tend to target the head, the neck and the areas behind the knees and around the waist
• Treating your pets (dogs) with tick repellents before going on a hike
• Inspecting, shaking out and, if needed, brushing off your clothes before bringing them into the house and wash them.

A number of insect repellents, some of which are also effective against ticks, are available on the market. They usually contain DEET (or N,N-diethyl-toluamide) and Icaridin (or KBR3023).

Ticks found on the skin should be promptly removed because the longer they are attached, the higher the risk of infection. After being attached and feeding for some time (a few hours), ticks regurgitate part of their meal back into the host’s bloodstream, along with any pathogen they are carrying. However, it should be noted that only a small proportion of ticks carry infectious agents.

Tick removal

What not to do:

• Never use alcohol, petrol, acetone, trichloroethylene, ammonia, oil, grease, heated objects, matches or cigarettes, as this could irritate the tick and cause it to regurgitate infected material and burrow deeper into the skin.

What to do:

• Using fine-tipped tweezers, grasp the tick as close to the skin as possible and pull it out gently while twisting slightly. Special tick extractors that allow removal of ticks with a rotating motion are currently available on the market
• Make sure not to squeeze the tick’s body, as this would cause regurgitation and increase the risk of infection
• After removing the tick, disinfect the bite site, but avoid using disinfectants that may cause staining of the skin, such as iodine tincture
• Avoid touching the tick with bare hands; protect your hands (with gloves) and wash them
• The tick’s mouthparts often remain embedded in the skin: if this is the case, remove them with a sterilized needle or sterilized fine-tipped tweezers
• It is advisable to place the removed tick in a jar of 70% alcohol to allow morphological identification and pathogen testing, if any symptoms develop, so that targeted treatment and appropriate medications can be provided. In case of illness, promptly inform your doctor of the date and location of the bite
• Have prophylactic treatment for tetanus
• Tell your doctor if you notice any of these symptoms: a red rash that tends to grow in size, fever, headache, weakness, joint pain, swollen lymph nodes.
• Use of antibiotics
• Use of systemic antibiotics during the observation period is not recommended, as it may mask signs of disease and make diagnosis more difficult. However, if treatment with antibiotics is needed, medications should be used that have shown to be effective in treating infectious diseases caused by Rickettsia and Borrelia bacteria.