Babesia - Clinical Presentation

Clinical Presentation

The severity of B. microti infections varies. For 25% of cases in adults and half of cases in children, the disease is asymptomatic or mild with flu-like symptoms. In cases of symptomatic infection, symptoms are characterized by irregular fevers, chills, headaches, general lethargy, pain, and malaise. In severe cases, hemolytic anemia, jaundice, shortness of breath, and hemoglobinuria are documented due to the lytic effects of parasitic multiplication. Immunocompetent individuals with healthy spleens often recover without treatment. Splenectomized patients are more susceptible to contracting the disease and the course of infection often ends fatally within five to eight days of symptom onset. Parasitemia levels can reach up to 85% in patients without spleens compared to 1-10% in individuals with spleens and effective immune systems. Splenectomized patients suffer from severe hemolytic anemia with occasional incidences of hepatomegaly and splenomegaly documented.

Complications arising from B. microti infections include acute respiratory failure, congestive heart failure, and renal failure. Infections can be fatal in 5-10% of hospitalized patients, with increased risk of death in the immunosuppressed, the elderly, and those coinfected with Lyme disease. B. divergens infections have a much higher fatality rate (42%) and present with more severe symptoms. Infected individuals suffer from hemoglobinuria followed by jaundice, a persistently high fever, chills, and sweats. If left untreated, B. divergens infections can develop into shock-like symptoms with pulmonary edema and renal failure.

Signs of infection usually arise one to eight weeks after a bite from an infectious tick. Infections from B. divergens have a shorter latent period, usually ranging from one to three weeks.

Bovine babesiosis caused by Babesia bovis remains an important constraint for the development of cattle industries worldwide. Effective control can be achieved by vaccination with live attenuated phenotypes of the parasite. However, these vaccines have a number of drawbacks, which justifies the search for better, safer vaccines. In recent years, a number of parasite proteins with immunogenic potential have been discovered. Through polymerase chain reaction, genetic sequencing and bioinformatics analysis of the genes, a high degree of conservation (98-100%) was found among Brazilian isolates of B. bovis and the T2Bo isolate. Thus, these genes are worth considering as viable candidates to be included in a recombinant cocktail vaccine for cattle babesiosis caused by B. bovis.