It is no secret that ticks transmit many diseases among which the well-known Lyme disease. Here are the diseases that can be contracted after a tick bite.
Ticks Basic facts
There are about 900 species of ticks in the world and like mosquitoes, they can spread diseases, some of which are difficult to treat. Ticks transmit pathogens through their saliva, which they inject when bitten. Their saliva also contains substances that inhibit the host’s immune system, creating an environment very conducive to the development of these pathogens. Each tick species is a vector for several diseases, and its ability to transmit a pathogen also depends on weather conditions or the frequency of the vector. Diseases that affect humans are discussed here, keeping in mind that ticks are also responsible for serious diseases in domestic and farm animals.
Why ticks are a good vector for transmitting diseases?
- The large amounts of blood they ingest increase the likelihood that they will acquire, store, and carry infectious agents.
- Many ticks feed on many different hosts, facilitating the transmission of pathogens from species to species.
- They have a long lifespan (up to several years for soft ticks), which helps keep pathogens in the wild.
- They reproduce very rapidly: up to several thousand eggs at a time for a female, maintaining a high tick population in the wild.
- They have a high dispersal ability through the movement of their host animals.
- Their saliva has anesthetic properties, so the bite goes unnoticed by most people.
NB: Even though ticks may not transmit infectious agents, they can still cause health problems just by biting. Some people may develop an allergy to their saliva or infection of the wounds caused by the bites.
1) Lyme disease
Infectious agent: Borrelia bacteria
Tick vector: ticks of the genus Ixodes (risk is greatest during their period of activity in spring and fall)
Incubation period: three to 30 days
Symptoms: in 60-80% of patients, the infection begins with erythema migrans (a red spot about 5 cm in diameter that spreads centrifugally). The disease can then progress to a disseminated phase, causing a wide range of symptoms such as facial paralysis, intermittent pain, severe headache, heart problems, neurological problems (dizziness, mental confusion, tingling sensation in hands or feet), and joint pain.
Rickettsioses that affect humans are Mediterranean fever and TIBOLA (tick-borne lymphadenopathy).
Infectious agent: Ricketta bacteria (R. Conorii, R. Slovaca, and R. Raoultii)
Tick vector: Rhipicephalus Sanguineus, Dermacentor Reticulatus, Dermacentor Marginatus
Incubation period: one to ten days.
Symptoms: a black spot at the bite site, followed by fever, fatigue, headache, rash. Mediterranean fever can develop into severe forms in 5-6% of cases, while Tibola usually causes no complications.
Infectious agent: Anaplasma Phagocytophilum
Tick vector: Ixodes ricinus
Incubation period: one to two weeks
Symptoms: flu-like syndrome (fever, chills, headache, muscle and joint pain), malaise, sometimes accompanied by digestive disturbances and rashes. Very rare fatal cases (about 1%) have been reported.
Transmission agent: bacterium Francisella tularensis
Tick vector: a large number of species can spread the disease, including Dermacentor Andersoni
Incubation period: three to five days
Symptoms: onset of fever, hepatosplenomegaly (enlarged liver and spleen), intestinal disorders, extreme fatigue. The disease can then develop into very different forms: ulcers, swollen lymph nodes, typhoid condition that can lead to atypical pneumonia. The mortality rate is about 6% when the disease is left untreated.
Infecting agent: Babesia Microti
Vector ticks: ticks of the genera Ixodes, Dermacentor, or Rhipicephalus
Incubation period: one to four weeks
Symptoms: in healthy people, the disease is usually asymptomatic. However, in immunocompromised patients, it can cause severe forms of the disease: high fever, multiple organ damage, anemia, hemoglobinuria, jaundice, and kidney failure. The mortality rate can be as high as 40%.
6) Tick-borne encephalitis (TBE)
Infectious agent: Flavivirus
Vector ticks: ticks of the genus Ixodes (the virus can be transmitted directly through bites or through raw milk products from infected animals).
Incubation period: one to two weeks.
Symptoms: flu-like syndrome followed by a febrile phase with neurological signs of varying severity in one-third of patients. In 5-15% of patients, the infection may spread to the brain and cause meningoencephalitis. Deaths are rare (less than 1%, mainly in the elderly).
7) Q fever
Infectious agent: Coxiella Brunetii bacteria
Tick vector: about 40 species of ticks can transmit the disease. The infection is spread mainly by inhalation of infected dust, especially among workers in close contact with livestock (who are asymptomatic hosts).
Incubation period: two to three weeks
Symptoms: 60% of patients are asymptomatic. In the remaining patients, the disease manifests itself mainly in three clinical forms: an influenza-like syndrome (fever, chills, headache, muscle, and joint pain), atypical pneumonia, and acute hepatitis. In 60% of patients, it is asymptomatic.