Co-infections

Anaplasma and Ehrlichia are gram-negative bacterial infections from the Rickettsiales genus which affect white blood cells. Anaplasma phagocytophilum causes human granulocytic anaplasmosis (HGA) and has been found in UK ticks although there has only been a single reported UK acquired case of human disease in Scotland.  Candidatus Neoehrlichia mikurensis (CNM) causes neoehrlichiosis and has also been found in UK ticks, with no confirmed reports of UK acquired cases of human disease.

Anaplasma and Ehrlichia can be transmitted through the bite of an infected tick, through blood transfusions or organ transplants and they can also be fatal in immunosuppressed patients. Both can be treated with doxycycline which is also used to treat Lyme disease.

Symptoms and complications: confusion, exhaustion, headaches, abnormal gait, ulcers, anorexia, abdominal pain, muscle pain (in particular shoulders and hips), fever, rashes, flu-like symptoms, jaundice, nausea, sweats, photophobia, conjunctivitis, enlarged liver, enlarged spleen, elevated liver enzymes, low white blood cell count, low platelet count, anaemia, myocarditis, renal failure, respiratory issues.

Babesia is a malaria-like parasite found worldwide but mostly commonly in the Northeastern and Upper Midwestern United States. In the US the primary species is Babesia microti, whilst in Europe it is Babesia divergens. In the UK, Babesia venatorum and Babesia divergens are the two main species thought to cause human disease, although very rarely. Whilst Babesia microti is a prominent cause of babesiosis worldwide, it is not common at all in the UK.

Babesiosis is primarily transmitted to humans through the bite of infected ticks. Over 100 species of Babesia carried by ticks have been identified but only a few are known to cause disease in humans. Babesia attacks and destroys red blood cells. The cell fragments can then lead to blocked capillaries and also put a strain on the liver and spleen. 

In 2006, The American Red Cross expressed concerns about the infection being spread via the blood supply. Babesia can also be transmitted from mother to fetus, and can prove fatal for anyone with a compromised immune system. Babesiosis is often treated with specific antibiotics, antiparasitic and antimalarial drugs. 

Symptoms and complications: night sweats, fevers, chills, lethargy, headaches (around the front of the head), cough, air hunger/shortness of breath, insomnia, fatigue, depression, anxiety, chest pain, hip pain, intolerance to heat and cold, agitation and suicidal ideation, encephalopathy, low blood pressure, low platelet count, jaundice, disseminated intravascular coagulation, haemolytic anaemia, renal failure, respiratory failure, congestive heart failure.

Bartonella is a gram-negative, intracellular bacteria. There are many species of Bartonella and there are at least 14 linked to disease in humans. While ticks can carry Bartonella, research is ongoing to establish their role in the spread of the disease to humans. Bartonellosis is also commonly associated with mosquitoes, fleas, lice, biting flies, and from the scratch of an infected cat (cat scratch disease). The infection may be passed from mother to fetus. 

Bartonellosis is associated with complex disease processes but it is possible to be chronically infected with Bartonella and not have disease symptoms. Symptoms can range from severe to chronic intermittent and often relapsing symptoms (see below). 

Bartonella takes up residence in the endothelial cells and from there attacks the red blood cells. It can affect the central nervous system and the brain, and is also believed to infect bone marrow. Inflammation of the vascular system can occur and effects of Bartonella have even shown up on SPECT scans as changes in the white matter of the brain.  Specific antibiotics including doxycycline may be used in combination to treat Bartonella. 

Symptoms and complications: raised papule and/or pustule on skin, stretch-mark type skin manifestations, neuropsychiatric issues, neuropathy, depression, anxiety, rage, sudden changes in mood, cognitive impairment, bone pain (shins, neck and back), subcutaneous nodules on extremities, low-grade fever, tremors, muscle twitching, fatigue, abdominal pain, seizures, burning or numbness on the soles of the feet, tingling and numbness, visual disturbances and other ophthalmological symptoms, balance problems, ataxia, irritable bladder, severe joint pain , swollen glands, headaches around the back of the head, conjunctivitis raised liver enzymes, endocarditis, myocarditis, gastritis, anaemia, bacillary angiomatosis and bacillary peliosis. 

Borrelia miyamotoi causes Borrelia miyamotoi disease (BMD) and is related to, but distinct from the type of Borrelia bacteria which causes Lyme disease. These bacteria belong to the relapsing-fever group in the spirochete genus of Borrelia. BMD cases have been reported in several regions including North America, Europe, and Asia. The bacteria are present in ticks in the UK although there have been no confirmed UK acquired human cases so far.

It is possible that BMD infections are going undiagnosed in the UK because routine blood tests may not distinguish them from Lyme disease. PCR testing may help to identify the bacteria’s DNA. Treatment is similar to that for Lyme disease and there is ongoing research to optimise treatment options.

Symptoms and complications: often presents as a nonspecific febrile illness, sometimes with symptoms resembling Lyme disease but without the characteristic erythema migrans (EM) rash. Common symptoms include a relapsing fever, fatigue, muscle and joint pain, headache, and nausea. Some patients may also experience raised liver transaminases, thrombocytopenia, or leukopenia.

Brucella is a gram negative intracellular infection which can potentially be acquired from a tick bite as the bacteria has been detected in ticks. It is however most commonly spread by consuming contaminated, unpasteurised milk or raw meat. The infection can also be caught by inhaling contaminated dust or through skin abrasion contact with infected animals or from handling contaminated blood samples. There have also been cases where Brucella has been spread from person to person sexually, in utero and via breast milk.

Found in countries across the Mediterranean region, the Arabian Peninsula, Africa, Asia, and Central and South America. Certain regions like the Middle East, sub-Saharan Africa, China, India, Peru, and Mexico show particularly high levels of animal brucellosis, which correlates with human cases. While rare in developed regions like Western and Northern Europe, Canada, Japan, Australia and New Zealand, some cases can occur due to travel or imported food products.

Brucella can affect every organ of the body and initially people can be asymptomatic. However, the infection can persist and recur and complications can be fatal. It is usually treated with specific antibiotic combinations.

Symptoms and complications: cyclical fevers, foul smelling sweat, headaches, urinary tract infections, joint pain, cough, gastrointestinal issues, weight loss, swollen glands, depression, enlarged spleen and liver, optic neuritis, endocarditis, meningitis, liver abscesses, arthritis, spondylitis.

Louping ill virus (LIV) is a flavivirus present in UK ticks but transmission to humans in the UK is rare. It is most commonly found in the Scottish Highlands and other upland areas with rough grasslands, including Wales, Cumbria and across the north of England. It is also found in Devon and other southwestern areas, and in Ireland. There have also been reports in Norway and Spain, Turkey, and Bulgaria, and related viruses have been identified in other parts of Europe and even Russia. 

The virus is primarily a disease affecting sheep and red grouse. Less commonly goats, cattle, deer, horses, dogs and pigs are affected. It can be transmitted to humans via a tick bite or contact with infected animal carcasses. There is currently no specific treatment for LIV infection in humans, and care is primarily supportive. 

Symptoms and complications: symptoms can vary and include a mild, flu-like illness with fever, headaches, muscle aches, and fatigue or encephalitis in severe cases. Very rarely a poliomyelitis-like illness and haemorrhagic fever has been reported.

Q fever is a gram negative intracellular infection caused by the bacteria Coxiella burnetii which can be transmitted via a tick bite. The disease is found worldwide, although relatively rarely in the UK, and not in New Zealand. It is most commonly reported in areas with significant livestock populations, particularly cattle, sheep and goats such as parts of Africa, Europe (especially the Netherlands, France, Spain and Greece), the USA (particularly the West and Great Plains) and parts of the Middle East. 

The bacteria is rarely spread by tick bites despite being found in over 40 species of tick. More commonly it is transmitted via consumption of or exposure to contaminated animal products, or by handling contaminated soil or animal bedding. Q fever can be transmitted sexually and from mother to fetus. 

People infected with Q fever are commonly asymptomatic or only show mild symptoms. However it can also cause chronic disease often involving cardiac complications, and can pose risks during pregnancy.

Doxycycline is the first-line treatment for acute Q fever, while chronic cases may require longer courses combined with other antibiotics.

Symptoms and complications: fevers, weight loss, muscle pain, sweats, muscle pain, joint pain, headaches, chills, confusion, dry cough, respiratory issues, nausea, gastrointestinal disturbances, meningoencephalitis, pneumonia, granulomatous hepatitis, liver enlargement, endocarditis, retinal vasculitis.

Rickettsiosis refers to a group of diseases caused by intracellular bacteria of the genus Rickettsia, transmitted to humans through the bite of infected arthropods like ticks, fleas, lice, and mites. 

Rickettsioses are found worldwide. Rickettsia helvetica is present in ticks in the UK, and there have been positive blood tests recorded in UK patients, however there have been no confirmed UK acquired human cases reported so far. These known cases were acquired overseas. Rickettsia infections respond to doxycycline which is also used to treat Lyme disease.

Symptoms and complications: a range of symptoms including fever, headache, muscle aches, rash, and potentially an eschar (a dark scab) at the site of the bite. Symptoms can be severe if left untreated.  Severe cases can involve the central nervous system and lead to complications such as confusion and breathing difficulties.  

Tick-borne encephalitis (TBE) is a viral infection transmitted by ticks belonging to the flavivirus genus. It can also be spread through unpasteurised milk or dairy foods. This infection affects the central nervous system.  Found in some European and Asian countries, TBE had been reported in travellers returning to the UK. The first confirmed case of TBE acquired in the UK was reported in 2022, following two suspected cases in 2019. The disease is currently considered to be rare in the UK. UK risk areas noted so far include Thetford Forest in the East of England, the Hampshire and Dorset border, the New Forest, the North Yorkshire Moors and Scotland.

There is no specific antiviral treatment for TBE. Treatment focuses on supportive care to manage symptoms and prevent complications. A vaccine is available for travel to high risk regions of the world.

Symptoms and complications: flu-like symptoms, fever, headache, fatigue, muscle pain, meningitis, encephalitis, cognitive dysfunction, seizures, photophobia, paralysis.

Toxoplasmosis is a parasitic disease found worldwide spread via ingestion of infected meat, contaminated unwashed vegetables and cat faeces. It can also be transmitted by a tick bite (uncommon), from mother to fetus and by blood transfusion or organ transplant. Often, people do not experience symptoms when they contract toxoplasmosis but for people with weakened immune systems, symptoms and complications can manifest. Complications can also occur if a woman is infected with toxoplasmosis during pregnancy such as miscarriages, stillbirths and birth defects.

Toxoplasmosis may resolve on its own but can also be treated with specific antibiotics, often in combination with other anti-parasitic medications.

Symptoms and complications: flu-like symptoms, skin lesions, hives, swollen glands, muscle aches, fevers, cognitive dysfunction, poor coordination, lung issues, visual issues, seizures.

Tularemia (also known as rabbit fever or deer fly fever) is an intracellular infection caused by the bacteria Francisella tularensis which can be transmitted by biting flies as well as ticks. It can also be acquired by handling infected small mammals such as rabbits, hares and rodents, by ingesting contaminated food or water, or by inhaling the bacteria. 

The disease is widespread in the Northern hemisphere. Key endemic areas include parts of North America and Canada, Scandinavia (particularly Sweden and Finland), Eastern Europe and Asia, particularly Russia, Japan, and Kazakhstan. Outbreaks have also been reported in a variety of other European countries, and in South Korea. The illness is still considered rare in Western Europe, and is not thought to be endemic in the UK.  However, a case of tularemia was reported in 2023 in a UK patient with no travel history or known bites before symptom onset. Monitoring of ticks continues.

Those infected may notice a lesion at the site of the bite which then forms a papule/ulcer and which has a black base. The illness can also cause very severe pneumonia. Treatment is usually with specific antibiotics.

Symptoms and complications: pneumonia, fatigue, signs of sepsis, skin ulcers, swollen glands, runny nose, chills, fever, headache, gastrointestinal issues, nausea, ulcers, conjunctivitis and other ophthalmological symptoms.