There is a diverse range of tick species around the globe, of which most are generalist feeders aggressively finding mammalian hosts to feed, including you and your beloved pets. Some tick species (mostly from the Ixodidae family), however, carry pathogens that can result in multisystemic lethal diseases in your pets, particularly in dogs. Although ticks are common and some are native to Hong Kong, there is a geographical distribution of tick species. More importantly, pathogens only infect certain tick species, so only a number of tick borne diseases are commonly found in Hong Kong. It is however worth mentioning that increased animal import and export, along with global warming, is having an impact on the geographical distribution of tick borne diseases.
Different Tick Borne Diseases:
1. Canine Ehrlichiosis:
It is caused by the intracellular bacteria of the Ehrlichia species transmitted by brown dog ticks (Rhipicephalus sanguineus). Different Ehrlichia species cause illnesses of various degrees. Some signs are nonspecific, including fever, lethargy, anorexia and depression. Acute infection by Ehrlichia leads to vascular inflammation and thrombocytopenia. The patients might also see melena, haematuria, bleeding from the gum, epistaxis, retinal haemorrhage, petechiation and ecchymosis. Infection by Ehrlichiaewingii and Ehrlichiachaffeensis can lead to polyarthritis, which might be manifested as lameness, stiffness, swelling or pain of the joints.
2. Canine Babesiosis:
Canine Babesiosis is a parasite commonly transmitted by brown dog ticks. Among the over 100 Babesia species, two – Babesia canis and Babesia gibsoni – are particularly important to Hong Kong’s dog population. For a tick to transmit the parasite to the host, it must feed on the host for at least 2-3 days. Following infection, the parasite infects and replicates within red blood cells, causing cell lysis. The immune system reacts by destroying these infected red blood cells, but doing so also destroys normal red blood cells, leading to a condition called immune mediated haemolyticanaemia (IMHA). Patients with Babesiosis often present with severe anaemia, resulting in pale gum, anorexia, weakness, fever, rapid heart rate and shortness of breath or even collapse. Some dogs might develop jaundice, with the tendency of petechiation and bleeding.
3. Lyme Disease:
It is caused by a bacteria named Borrelia burgdorferi transmitted with the prolonged attachment (>50 hours) of Ixodes ticks. Most dogs can mount immune responses to the infection and remain asymptomatic. Around 5% of infections result in acute polyarthritis. Cardiac, renal and neurological signs are also seen with Lyme Disease. Shetland Sheepdogs, Golden Retrievers and Labradors have higher risks of developing renal failure with Lyme Disease, which is often lethal.
4. Anaplasmosis:
Anaplasmaphagocytophilum is a rickettsial agent transmitted by Ixodes ticks. A tick must attach to the host for at least 24-48 hours to transmit the parasite. Most infections result in nonspecific signs, such as fever, lethargy, anorexia, vomiting and diarrhoea. Some dogs experience stiffness, lameness and possibly polyarthritis. Infections affecting the central nervous system, spleen and liver have been reported as well.
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