Treatment and control
It is difficult to totally eradicate ticks , especially twoor three-host ticks , as there will be reintroduction by other hosts , such as migratory birds or by bringing infected animals into the area [ 6 ] . If the ticks are threehost parasites , the treatment needs to be repeated on several potential host animals . Therefore , ticks may be managed but are unlikely to be eradicated .
It is worth noting that if ticks were ( almost ) eradicated , the hosts would have less exposure to them and therefore have a reduced immune response to the diseases they carry .
Resistance can develop when acaricides are frequently used . In the past , animals were often dipped in a solution of acaracide , but these were potentially harmful to people and the environment , so now spoton treatments are generally used . It is important to consider the timing of treatment – for example , spring if treatment is focused on the nymph stage , as this is when nymphs will emerge .
Pasture rotation for grazing animals may help if the area can be left for more than 4 months , killing off unfed larvae . However , larvae can still feed on small mammals and birds , so this approach is less effective for two- or three-host ticks .
Tick vaccines have been developed ( e . g . TickGARD ® ) but these tend to be expensive and tick-specific , so they are often used only in particularly tick-ridden regions , such as Australia , and are not yet available in the UK . The tick needs to feed to ingest the antibodies raised by the vaccine , and frequent boosters are required because tick feeding does not reinforce the vaccine immune response ( the antigen – antibody reaction occurs in the tick rather than the host ).
There are repellents available for humans , which can be effective if sprayed on clothes or skin , depending on the product , and may be used off-licence on animals .
An alternative solution is herbal tick control , where supplements ingested by the host have a detrimental effect on tick survival .
Babesiosis
The blood-borne protozoan Babesia spp . can affect many species , including dogs , cats , cattle and horses . It resides in the red blood cells , making it an intraerythrocytic protozoan , and has many species , such as B . canis , B . felis , B . bovis and B . caballi . It is prevalent around the world and there have recently been numerous cases in the UK . The tick genus Dermacentor spp . in northern Europe , and occasionally the UK , is a vector for B . canis .
Pathogenesis
The severity of the disease is dependent on the strain and external factors , such as the age of the host and its immune system capabilities . Europe tends to have the less virulent species , lower numbers of ticks and lower incidence of clinical signs , compared with the sub-tropics .
Virulence tends to be more severe in young dogs infected by B . canis canis and B . canis rossi .
Clinical signs
Parasitaemia , when the protozoa are in the circulation , may cause fever and , as the parasite destroys the red blood cells , it can cause haemolytic anaemia , resulting in a low packed cell volume ( PCV ). There are two types of babesiosis based on clinical signs : uncomplicated and complicated ( Table 1 ).
Table 1 . Clinical signs of the two types of babesiosis .
Uncomplicated form Anorexia
Fever
Anaemia Jaundice Haemoglobinuria Lethargy
Symptoms are also dependent on whether the disease is peracute , acute or chronic ( see Table 2 , overleaf ). Depending on the organ / system involvement , other clinical signs may include :
• Oedema
• Ascites
• Gastritis
• Dyspnoea
• Epilepsy .
Diagnosis
Complicated form
Cerebral clumping causing neurological signs
High mortality rate of over 80 %
Diagnosis is based on clinical signs , the presence of ticks on the animal or in the area , and analysis of investigations such as PCR and ELISA tests .
Volume 38 ( 2 ) • April 2023
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