Introduction

• Cause:
  • Babesia divergens is responsible for clinical disease in temperate Europe and the U.K. and is spread by the sheep tick, Ioxodes ricinus.
  • Babesia bigemina is responsible for clinical disease in Africa, Australia, Southern Europe, Central and Southern America.
  • Although not present in the UK, Babesia bovis, is found throughout the world where boophilus ticks proliferate, in particular Southern Europe.
  • Babesia major is a non-pathogenic species found in South East England.
• Signs: pyrexia, pallor, tachycardia, tachypnea, hemolytic anemia, icterus, hemoglobinuria and death. Cattle with the chronic form may suffer from marked emaciation, depressed milk yields and abortion.
• Diagnosis: demonstration of the organism on blood or tissue smears using Giemsa stain.
• Treatment: imidocarb (1-3 mg/kg) via the subcutaneous route.
• Prognosis: guarded.

Pathogenesis

Etiology

• Cattle and the tick hosts serve as the main reservoir of infection.
• Clinical disease is almost always transmitted by ticks, but like other blood borne diseases, iatrogenic transfer via needles or surgical interventions is possible.

Predisposing factors

General

• Naïve cattle introduced into an endemic area.
• Infected cattle introduced into an uninfected area.
• Cattle grazed on rough grazing.
• Infected ticks transported on cattle or wildlife such as deer into an uninfected area.
• Physiological stress, for example, malnutrition, transportation or parturition.
• There is an increased incidence of disease during periods of peak tick activity, namely the Spring and Autumn.

Pathophysiology

• After inoculation as sporozoites, the parasite enters the erythrocytes and undergoes further division into trophozoites and then merozoites Ticks: overview.
• Rupture of the erythrocytes occurs with emergence of the merozoites and the classical signs of the disease.
• Ticks become infected by feeding on infected cattle and the parasites are passed onto the ovaries of the ticks so that all new generations of ticks are infected.

Timecourse

• Clinical signs manifest 2-3 weeks after tick infestation.

Epidemiology

• Passively acquired resistance from colostrum Colostrum: overview lasts about 2 months but is followed by innate immunity to babesiosis from 3 to 9 months of age.
• In endemic regions calves are usually exposed to babesia between 3-9 months of age and rarely develop clinical disease followed by long term immunity of up to 4 years duration. However, should calves fail to be exposed within this 3-9 month window for example following a decrease in infected tick numbers, endemic instability will ensue, making these calves susceptible to disease outbreaks later in life.

Diagnosis

Treatment

Prevention

Outcomes