Genetic Analysis of Babesia Isolates from Cattle with Clinical Babesiosis in Sri Lanka

Bovine babesiosis is a serious threat to the cattle industry. We prepared blood DNA samples from 13 cattle with clinical babesiosis from the Badulla (n = 8), Jaffna (n = 3), and Kilinochchi (n = 2) districts in Sri Lanka. These DNA samples tested positive in PCR assays specific for Babesiabovis (n = 9), Babesia bigemina (n = 9), and Babesiaovata (n = 1). Twelve cattle were positive for B. bovis and/or B. bigemina One cow was negative for the tested Babesia species but was positive for Babesia on microscopic examination; the phylogenetic positions of 18S rRNA and cytochrome oxidase subunit III gene sequences suggested that the cow was infected with Babesia sp. Mymensingh, which was recently reported from a healthy cow in Bangladesh. We then developed a novel Babesia sp. Mymensingh-specific PCR assay and obtained positive results for one other sample. Analysis of gene sequences from the cow with positive B. ovata-specific PCR results demonstrated that the animal was infected not with B. ovata but with Babesia sp. Hue-1, which was recently reported from asymptomatic cattle in Vietnam. The virulence of Babesia sp. Hue-1 is unclear, as the cow was coinfected with B. bovis and B. bigemina However, Babesia sp. Mymensingh probably causes severe clinical babesiosis, as it was the sole Babesia species detected in a clinical case. The present study revealed the presence of two bovine Babesia species not previously reported in Sri Lanka, plus the first case of severe bovine babesiosis caused by a Babesia species other than B. bovis, B. bigemina, and Babesiadivergens.

Age distribution of naturally occurring acute babesiosis in cattle in Sweden

The age distribution of clinical cases of babesiosis reported by local veterinary practitioners was investigated in 1976 and 1981. The first study was based on material collected primarily for identifying the Babesia species, the second on computerized reports from a part of one county in Sweden.

The results were similar. Most diseased animals, 135/165 (82%) and 145/161 (90%) respectively, were more than 2.5 years old (cows), while 27/165 (169b) and 12/161 (8%) respectively, were 1–2.5 years old and only 3–4 (2–3%) animals were calves less than 1 year old. This age group, however, probably did not meet the same infection risk as did older animals. Among cows (>2.5 years old) there seemed to be no influence of age on the distribution of clinical babesiosis. Calculation based upon the entire animal population of the county investigated in 1981 revealed that clinical babesiosis was reported about 11 times more often among cows than among heifers and steers. The comparatively high resistance among 1–2.5 year–old cattle may be a function of an inverse age resistance, and/or may be influenced by vaccination against babesiosis on »high risk« farms in Sweden and a lower risk of infection on other farms such that animals tend to escape infection prior to adultness. Babesia organisms were found in 156 of 165 cases (95%) reported as clinical babesiosis.

First Autochthonous Report on Cattle Babesia naoakii in Central Java, Indonesia, and Identification of Haemaphysalis bispinosa Ticks in the Investigated Area

In tropical countries, clinical bovine babesiosis is a tick-borne disease primarily caused by Babesia bovis and Babesia bigemina. Here, we investigated 11 cattle with presumptive diagnosis of clinical babesiosis in Boyolali district, Central Java, Indonesia. The majority of the animals were anemic, as evidenced by lower hematocrit, hemoglobin concentration, and red blood cell counts than the normal ranges. Blood DNA was analyzed by a PCR assay targeting the 18S rRNA-ITS region of babesial origin, and the results confirmed that the cattle were infected with Babesia species. The sequencing and phylogenetic analyses demonstrated that the animals were infected with Babesia naoakii. This is the first report of B. naoakii in Indonesia and of B. naoakii-induced clinical bovine babesiosis outside of Sri Lanka. B. naoakii causes a persistent infection, as indicated by positive PCR results for serial blood samples of the circulatory system taken two weeks after treatment. Consequently, subclinical or newly recovered cattle may serve as potential intermediate hosts and infect ticks as definitive hosts to complete the life cycle. To identify potential tick vectors, we collected ticks from cattle, including 11 animals with clinical babesiosis. Based on the morphology and the mitochondrial cytochrome c oxidase subunit 1 (COX1) of collected ticks, we found that all of the collected ticks were Haemaphysalis bispinosa, identifying this tick species as a potential vector of B. naoakii in Indonesia. In this study, the evaluation of local farmers' awareness and practices regarding tick-borne diseases is presented, as disease prevention is also reliant on the implementation of strategies for vector control. Since livestock activities in Java represent the country's busiest animal trade, thereby the spread of disease to other regions is possible through anthropogenic factors. In conclusion, B. naoakii is a causative pathogen of clinical bovine babesiosis autochthonously occurred in this report and further research on B. naoakii-infection is required in other regions of the country. The prompt treatment of the disease seemed crucial for animal survival, which implies the necessity of early diagnosis and a sensitive detection method.

Inverse age resistance to experimental Babesia divergens infection in cattle

Two groups of calves, 1.5-2 and 7-11 months old respectively, and dairy cows were inoculated i.v. with 3 x 10(7) erythrocytes infected with Babesia divergens. High parasitaemia, fever and other clinical signs of babesiosis occurred among adult animals. A very low parasitaemia and a slightly increased body temperature but no other symptoms occurred in calves. these findings substantiate the conclusion that there exists an inverse age resistance against Babesia divergens. The kinetics of B. divergens IgG antibody formation were similar in all age groups. Consequently this antibody response was not the factor determining the development of the primary parasitaemia and thus the inverse age resistance phenomenon. However, age is not necessarily the only factor involved in the clinical expression of babesiosis. The kinetics of antibody formation was not associated with the intensity of the parasitaemia. In fact only about half the animals had a demonstrable parasitaemia although the antibody responses were similar in all age groups.