Diseases transmitted by ticks

I have found a tick on my pet, can I have it identified?

Ticks can be sent to the Tick Recording Scheme (TRS), who can identify the species of tick found on your pet, which may help decide which infections the tick may be carrying.  This service is free of charge and further details about the safe removal of ticks and sending ticks for identification are available on their website. The TRS also provides important information regarding ticks found on travelling and imported dogs, particularly regarding the brown dog tick, which is non-native to the UK but can transmit human and animal diseases. This tick has been found on travelled dogs in the UK and can survive indoors. More information can be found here.

 

Babesiosis

What is babesiosis?

This is a disease caused by a range of different protozoan parasite species including so-called large Babesia species (e.g. Babesia canis) and so-called small Babesia species (e.g. Babesia gibsoni). They are transmitted by ticks of several species, around 24-48 hours after tick attachment, and are tropic for red blood cells, causing anaemia but also thrombocytopenia.

Canine babesiosis has a global distribution commonly affecting domestic dogs in Africa, Europe and Asia. Young to middle-aged dogs may be more predisposed, although any dog which does not have immunity is predisposed. Although ticks are the major means of transmission, there have been reports of transmission of some Babesia species by blood transfusions and biting.

It appears that dogs with some immunity may remain carriers for years, and stress or other diseases may induce sudden onset of clinical signs of weakness and collapse.

FAQs

Does canine babesiosis occur in the UK?

The vast majority of dogs diagnosed with babesiosis in the UK have travelled abroad or have been imported. However an outbreak of B. canis infection in untravelled dogs has been reported recently in Essex, and B. canis-infected Dermacentor reticulatus ticks have been found in that area of Essex too. Cases of other Babesia species infections in untravelled UK dogs have also occasionally been reported (e.g. B. microti-like, B. vogeli) so the disease should remain a differential diagnosis for UK dogs with thrombocytopenia, regenerative anaemia and pigmenturia if they have not travelled.

What are the clinical signs of babesiosis?

These usually develop within a few days of infection. Signs can include fever, lethargy, weakness, pallor, jaundice and pigmenturia (red urine due to haemoglobinuria) and collapse in severe cases. Splenomegaly is common. Multiple organ failure can occur with some babesia infections.

What clinical pathology changes occur with babesiosis?

Thrombocytopenia is very common. An anaemia, usually regenerative in nature due to direct haemolysis of the red blood cells by the parasite, and sometimes associated with erythrocyte antibodies (i.e. positive autoagglutination or a positive Coombs’ test), is also often found.

Can blood smears diagnose Babesia species infection?

Sometimes infection with a large Babesia species may be identified on blood smear examination but they are often hard to spot. Making a blood smear from blood collected from a capillary e.g. on the ear margin, may help concentrate large Babesia organisms as heavier parasitized erythrocytes are more likely to be marginated in peripheral capillaries. Generally blood smear examination is not very sensitive. Small Babesia species are very difficult to spot on blood smears.

Is PCR useful for the diagnosis of babesiosis?

Yes, PCR is reliable and is usually performed on blood samples. The Acarus laboratories of the Molecular Diagnostic Unit has a generic Babesia spp. QPCR that amplifies all Babesia species (large and small) followed by identification of the infecting species by sequencing. Knowledge of the infecting species is important as treatment differs for different Babesia species.

Is serology useful to diagnose babesiosis?

Not really. Cross-reactivity between the different Babesia species occurs, which is problematic, and not all parasitaemic dogs are antibody positive.

How do I treat babesiosis?

Treatment depends on the infecting species and clinical presentation, with large Babesia species generally being easier to treat than small Babesia species. No product is licensed for use in dogs for babesiosis in the UK. Imidocarb diproprionate is used in cattle for babesiosis so a small amount may be available from large animal vets to treat dogs with large Babesia species infections.
*Drugs are not licensed for this purpose in the UK
Babesiosis type Drug Treatment protocol Possible side Effects
Large Babesia species e.g. Babesia canis, Babesia vogelis, Babesia rossi *Imidocarb diproprionate 6.6 mg/kg IM or SQ (if severe thrombocytopenia) once,
then repeat 2 weeks later
Uncommon but cholinergic side effects sometimes seen e.g. salivation, lacrimation, diarrhoea, vomiting – can pretreat with atropine if concerned. Usually results in PCR negative results on blood.
Small Babesia species e.g. B. gibsoni, B. microti-like (also known as Theileria annae) Ataquavone plus azithromycin Seek advice from a specialist
before starting a 10 day treatment course.
Very difficult to clear infection and treatment not always effective. Some have used doxycycline/ metronidazole/ clindamycin or diminazine/ imidocarb/ clindamycin protocols for B. gibsoni infection.
Concurrent Ehrlichia canis infection Doxycycline 10 mg/kg/d PO E. canis and B. vogeli are both transmitted by the same tick vector so concurrent ehrlichiosis is treated with doxycycline. Doxycycline may have some activity for small Babesia species and is sometimes used for B. gibsoni infections.

 

How do I prevent babesiosis?

Effective tick control! Owners should be instructed to avoid tick exposure whenever possible, remove any ticks found on a dog promptly and use a topical ectoparasiticide that is effective against ticks. A vaccine is available for babesiosis in some parts of the world, but not in the UK.

What about cats?

Cats are less commonly affected by babesiosis than dogs and cases thus far in the UK have been restricted to imported cats. Babesiosis is most commonly reported in cats in South Africa due to Babesia felis infection (a small Babesia species). Diagnosis is based on PCR analysis of blood samples. Advice should be sought regarding treatment which comprises primaquine.

Bartonellosis

Bacteria of the genus Bartonella are found in the blood of many wild rodents and larger mammals, such as deer, throughout the world. In these natural hosts, infection with the bacteria does not appear to influence fitness. However, the transfer of these bacteria to domestic animals and humans can result in disease.

Bartonella appear to be transmitted from one animal to another by a range of biting insects, particularly fleas, although ticks have also been implicated. The disease can also pass, to humans at least, by direct inoculation e.g. by scratching or biting by heavily infected animals (thus giving rise to "cat scratch disease" a problem in immuno-compromised humans).

Bartonellosis (infection with Bartonella) is largely an infection of cats where it causes a wide spectrum of problems dependent on the underlying health of the animal, although current work is investigating its association with disease in other companion animal species. It appears that many animals carry Bartonella but remain symptomless. When stressed or immuno-compromised cats may develop fever, anaemia, heart and liver problems and neurological signs.

 

FAQs

What are the clinical signs?

It appears that many animals carry Bartonella but remain symptomless. When stressed or immuno-compromised cats may develop fever, anaemia, heart and liver problems and neurological signs.

Borrelia burgdorferi sensu lato infection (the cause of Lyme disease)

What is B. burgdorferi s.l.?

These comprise a group of genospecies of spirochaete bacteria (primarily Borrelia burgdorferi sensu stricto, Borrelia afzelii and Borrelia garini) that cause Lyme disease in a small percentage of infected dogs. They are found worldwide including the UK, and are transmitted by the tick Ixodes ricinus, also found in the UK. Recent surveys have found that 2.3% of ticks in the UK were B. burgdorferi s.l. infected. Transmission from the tick to the host occurs about 36 to 48 hours after the tick starts feeding.

Pictured left: I. ricinus is the tick vector for B. burgdorferi s.l., the agent that can cause Lyme disease in dogs
 

FAQs

What clinical signs are seen with B. burgdorferi s.l. infection?

A rash may occur where the tick attached to the dog, but no ‘bullseye’ lesion is seen in the skin as is common in humans infected with B. burgdorferi s.l. In dogs which show clinical signs, these usually develop around 2-5 months after a tick bite and comprise lethargy, fever, polyarthritis and lymphadenopathy. Signs may be worse in young or immunocompromised dogs.  Occasionally cardiac, neurological or renal signs are reported.

 

What clinical pathology changes occur with B. burgdorferi s.l. infection?

There are no real characteristic haematology or serum biochemistry changes in B. burgdorferi s.l. infection. A mild thrombocytopenia may be present. In the USA Lyme nephritis is reported, particularly in Labradors and Golden Retrievers, with associated azotaemia and proteinuria, but this is not recognised in the UK.

 

Is PCR useful for the diagnosis of B. burgdorferi s.l. infection?

Not often! PCR is sensitive and specific but the organism needs to be present in the sample submitted for PCR to able to identify it. B. burgdorferi s.l. is not present consistently in the blood of infected dogs, including those with clinical illness so blood samples for PCR are not that useful. Synovial fluid (or synovial membrane) samples from dogs with joint changes will offer increased sensitivity for PCR analysis. If a tick bite has been identified, a skin biopsy taken adjacent to the tick bite can also be submitted for PCR.

 

Is serology useful to diagnose B. burgdorferi s.l. infection?

Yes. As outlined above, finding B. burgdorferi s.l. by PCR is difficult but infected dogs will usually seroconvert and mount an antibody response. However this occurs in both asymptomatic infected dogs as well as those with clinical Lyme disease, so seropositivity does not equate with disease. The Idexx SNAP4Dx test detects antibodies specific for B. burgdorferi s.l. (most genospecies are believed to be detected although it may not pick up all strains of B. afzelii) and thus can be used as a screening test for Lyme disease in dogs. A positive result may need to be followed up with a quantitative antibody test for B. burgdorferi s.l.

 

How do I treat B. burgdorferi s.l. infection?

Doxycycline (10 mg/kg SID PO) is the treatment of choice for Lyme disease with 4 weeks of treatment usually recommended with a good response to treatment seen, usually starting within 48 hours. Intensive therapy is required for Lyme nephritis which carries a guarded prognosis.

 

How do I prevent B. burgdorferi s.l. infection?

Effective tick control! Owners should be instructed to avoid tick exposure whenever possible, remove any ticks found on a dog promptly and use a topical ectoparasiticide that is effective against ticks. There is also an inactivated whole cell B. burgdorferi s.l. vaccine available in the UK which can be considered for dogs living in areas known to have a high risk of Lyme disease.

 

Is B. burgdorferi s.l. zoonotic?

Infected dogs do not pose a direct zoonotic risk to humans but humans can develop Lyme disease following a tick bite with B. burgdorferi s.l. infection. A bullseye rash occurs within a month of the tick bite, moving outward from the bite site over time. Cardiac and neurological signs can develop as well as arthritis.

 

What about cats?

Lyme disease has not been reported as a clinical entity in cats although evidence of infection with B. burgdorferi s.l. in cats has been reported worldwide, including in the UK.

 

Ehrlichiosis

Monocytes infected with Ehrlichia canis

Ehrlichiosis is caused by tick-transmitted intracellular bacteria that invade monocytes and macrophages (Ehrlichia canis) and in some cases, platelets (Anaplasma, previously Ehrlichia platys. The most common and important species affecting dogs is E. canis. It is transmitted by the tick Rhipicephalus sanguineus, which is well adapted to kennels, houses and cars. It has been reported from the USA, Europe and Africa.

German Shepherds are predisposed to serious disease and may develop a fatal form of infection. Transmission by blood transfusion also occurs.

 

 

FAQs

What are the clinical signs?

A dog with ehrlichiosis and haemorrhage in the eye.

Clinical signs include intermittent fever, lymphadenopathy, bleeding (petechiation, haematuria, epistaxis, retinal haemorrhage), weight loss, severe eye disease, other signs of immune-mediated disease and bone marrow hypoplasia subsequent with cytopenias.

Thrombocytopenia is marked and platelet function is also impaired. Excessive antibody production leads to high protein levels and may result in hyperviscosity syndrome

 

 

How do I diagnose Erlichiosis?

Diagnosis is made by demonstration of organisms in white blood cells, or by specific PCR on a peripheral blood sample or splenic aspirate. Serological testing is available but cross-reactions may occur with other ehrlichial organisms and two samples one month apart are required to confirm active infection.

What treatment options are there?

Doxycycline is the treatment of choice for ehrlichiosis and response in the early stages of infection is reported to be excellent. Antibiotic therapy should be administered for a minimum period of 28 days (Table 2). There is no vaccination but the disease may be prevented by aggressive tick control (Table 4).  Ehrlichia canis does not cause disease in humans but some of the less common ehrlichial species found in the US are zoonotic
Ehrlichiosis Drug Treatment protocol Side Effects
Cyclic
thrombocytopenia
Doxycycline 5-10mg /kg PO
q12-24 for 14-21 days
Staining of teeth not as much of a problem as for oxytetracycline. Oesophagitis if incomplete swallowing with some formulations in cats