lmidocarb dipropionate is a derivative of the carbanilide antiprotozoals. Although the exact mode of action of the drug is not known, a possible mechanism is interference with cellular repair and replication through binding with DNA. lmidocarb is highly effective against infections caused by Babesia and Anaplasma spp.
Babesiosis, also known as tick fever or redwater, is caused by tick-borne protozoal parasites of the genus Babesia. Babesiosis is characterised by fever, anaemia, icterus and haemoglobinuria. It is a widespread disease most common in tropical regions where the cattle tick Rhipicephalus(Boophilus) decoloratus and Rhipicepha/us (Boophilus) microplus is abundant. The most significant parasites causing Babesiosis in cattle are Babesia bovis and Babesia bigemina.
In endemic areas infection with Babesia is acquired by calves at a young age but infection does not manifest as clinical disease due to natural resistance. Animals infected early act as carriers of infection, remaining immune to clinical disease as long as infection persists. Re-infection constantly occurs in endemic areas. Without re-infection, immunity is lost within several months and clinical disease results.
Clinical disease most commonly occurs when:
- susceptible cattle are transported from a non-endemic to an endemic region
- contact occurs between infected and non-infected cattle
- epidemics occur following introduction of infection to non-endemic areas or sudden increases in tick populations where environmental conditions are favourable
- the tick vector population drops due to altered weather patterns or tick control measures reducing re-infection rate and therefore immunity
Treatment of clinical cases of Babesiosis with lmidox® is most effective when cattle are treated early in the course of the disease and in combination with supportive therapy such as provision of shade.
Where disease is severe, repeat treatment with lmidox® may be required after 24 hours.
Sterilization of infection with lmidox® results in complete elimination of Babesial parasites from carrier animals. Elimination of carriers is necessary where movement of cattle from an endemic to a non-endemic area would otherwise result in infection of susceptible cattle.
Prevention of Babesia infection may be achieved by treatment of susceptible animals with lmidox® prior to introduction into an endemic area. Over time the level of imidocarb in the animal's body diminishes, allowing a small number of parasites to establish infection while the animal is still protected by the drug. The result is the development of immunity to disease without the occurrence of clinical signs. However if there is no exposure to infection during the period of weaning imidocarb levels, the animal will become susceptible to clinical disease. One dose of lmidox® will provide protection from infection for up to 4 weeks. lmidox® is useful for the protection against Babesiosis where a short passage through an endemic area is planned for a herd of susceptible cattle. Outbreaks of Babesiosis may be controlled by administration of preventative doses of lmidox® to all animals exposed to infection, however vaccination will still be necessary at a later time.
Anaplasmosis is a tick-borne disease caused by the rickettsial organism Anaplasma marginalewhich parasitisises red blood cells. The course of the disease may be prolonged over months. The severity of disease resulting from infection tends to increase with age, reaching up to 50 % mortality in susceptible adult cattle.
The clinical signs of Anaplasmosis relate to the acute anaemia that results and include fever, jaundice and emaciation. Decreased milk production and abortion are common. The clinical signs of Anaplasmosis and Babesiosis are very similar, however the dose rate for their treatment differs. It is therefore important to prepare blood smears from suspect cases for laboratory examination in order to distinguish between them.
lmidox® is an effective treatment for Anaplasmosis at the recommended dose rate. Supportive therapy should be instituted including provision of shade and plenty of feed and water. In severe cases blood transfusion may be required. Recovered animals should be monitored for approximately 4 weeks following treatment, as re- treatment may be necessary if relapse occurs.
To reduce risk of transmission of the disease the herd should be dipped several times for tick control.
