Cost-effectiveness of Babesia microti antibody and nucleic acid blood donation screening using results from prospective investigational studies.

BACKGROUND: Babesia microti causes transfusion-transmitted babesiosis (TTB); currently, blood donor screening assays are unlicensed but used investigationally. STUDY DESIGN AND METHODS: We developed a decision tree model assessing the comparative- and cost-effectiveness of B. microti blood donation screening strategies in endemic areas compared to the status quo (question regarding a history of babesiosis), including testing by: (1) universal antibody (Ab), (2) universal polymerase chain reaction (PCR), (3) universal Ab/PCR, and (4) recipient risk-targeted Ab/PCR. The model predicted the number of TTB cases, complicated TTB cases, cases averted, and quality-adjusted life years (QALYs). Economic outcomes included each strategy's per-donation cost, waste (number of infection-free units incorrectly discarded), and waste index (number wasted units/number true positives). Sensitivity analyses examined uncertainty in transmission probabilities, prevalence rates, and other key model inputs. RESULTS: Universal PCR in four endemic states would prevent 24 to 31 TTB cases/100,000 units transfused (pht) at an incremental cost-effectiveness ratio (ICER) of $26,000 to $44,000/QALY (transmission probability dependent) and waste index of zero. Universal Ab/PCR would prevent 33 to 42 TTB cases pht at an ICER of $54,000 to $83,000/QALY and waste index of 0.05. The questionnaire is most wasteful (99.62 units wasted pht; 208.62 waste index), followed by the risk-targeted strategy (76.27 units wasted pht; 0.68 waste index). The model predicted zero cases of TTB or complicated TTB with universal Ab/PCR (versus [33, 42] and [13, 18] pht, respectively [no screening]). Results are highly sensitive to transmission probabilities. CONCLUSIONS: Universal PCR in endemic states is an effective blood donation screening strategy at a threshold of $50,000/QALY. Using a higher cost-effectiveness ratio, universal Ab/PCR is the most effective strategy.

Comparison of indirect fluorescent antibody test (IFAT) and slide enzyme linked immunosorbent assay (SELISA) for diagnosis of Babesia bigemina infection in bovines.

An indirect fluorescent antibody test (IFAT) and slide enzyme linked immunosorbent assay (SELISA) were standardized for the detection of antibodies specific to Babesia bigemina in experimentally infected bovine calves and subsequently used for the screening of naturally infected bovine and bubaline sera. In experimentally infected calves positive reactivity was detected in sera at the earliest on day 7 by both the tests. Serological studies for detection of B. bigemina specific antibodies in 180 cow and 120 buffalo serum samples procured from endemic zones of Uttar Pradesh and Punjab revealed 56.11% and 23.33% seropositivity, respectively, both by SELISA and IFAT. Variation in the reactivity pattern between these tests was found to be non significant. The sensitivity of SELISA was determined to be 94.85% whereas the specificity was 90.85% in comparison to IFAT. The agreement between the two tests by kappa statistics at 95% confidence interval revealed kappa- value of 0.853 that depicts almost a perfect degree of agreement. The findings employing experimental as well as test sera from cattle and buffalo from some of the tick infested zones of India suggested that SELISA could be a useful tool for seroprevalence studies on babesiosis, as the test is less cost intensive with high levels of sensitivity and specificity.

Prevalence of blood parasites in cattle from wilayates of Annaba and El Tarf east Algeria.

Between June and September 2002, a preliminary study was conducted to assess the prevalence of blood parasites of cattle in eastern Algeria. Fifty-four bovines of different genotypes were submitted to clinical examination. From each animal, blood smears were made and stained by Giemsa. Four species of parasites, namely Theileria annulata, T. orientalis, Babesia bovis and Anaplasma marginale were encountered. Fifty animals carried single or multiple infections with blood parasites and four were found negative. The rate of single infections (72.3%, n = 39) was almost three times higher than multiple infections (20.3%, n = 11). The high percentage of single infections was recorded with T. annulata (53.7%). However single infection with Anaplasma marginale (7.4 %), B. bovis (5.6%) and T orientalis (5.6%) were very low compared to T. annulata infection. The rates of mixed infection were as follows: T. annulata/A. marginale 9.3%, T. annulata/T. orientalis 5.6%, A. marginale/T. orientalis 3.7% and B. bovis/A. marginale 1.9%.

Changes in haematocrit after treatment of uncomplicated canine babesiosis: a comparison between diminazene and trypan blue, and an evaluation of the influence of parasitaemia.

It has been suggested that the antibabesial drug diminazene causes a rapid decline in haematocrit after treatment of dogs with high Babesia canis parasitaemias, compared with trypan blue. To test this, 19 dogs with clinically mild to moderate, uncomplicated babesiosis were placed in low, moderate or high parasitaemia groups, based on venous parasitaemias, and were allotted randomly to diminazene or trypan blue treatment groups. Haematocrit and parasitaemia were determined before treatment, and at 2, 6, 12, 18 and 24 hours. The drugs were compared for effects on haematocrit and parasite clearance. Changes in haematocrit after treatment were analysed. There were no significant differences between diminazene and trypan blue for haematocrit or parasite clearance. There was no correlation between initial parasitaemia and initial or post-treatment haematocrit. In all dogs, haematocrit fell following treatment. The maximum mean reduction from the baseline (0 h) was 0.046 l/l (range 0.02-0.07 l/l); this most often occurred at 6 or 12 h. The 24 h haematocrit ranged from 70.5-113.6% of baseline (mean absolute haematocrit 0.019 l/l below baseline). All dogs improved clinically during the study period. It was concluded that either diminazene or trypan blue can be safely used to treat dogs with clinically mild or moderate, uncomplicated babesiosis. Parasitaemia need not be taken into account when deciding which antibabesial drug to administer and does not appear to be related to the degree of anaemia.