Cryopreservation of Babesia divergens from jirds as a live vaccine for cattle

Babesia divergens, a bovine blood parasite of veterinary and zoonotic importance

Babesia divergens is an intraerythrocytic protozoan parasite, transmitted by the tick Ixodes ricinus, and is the main agent of bovine babesiosis in Europe. It is not only a cause of significant loss to the cattle industry; it can also infect immunocompromised humans, causing medical emergencies characterized by rapid fulmination and parasitemias that may exceed 70%. The current emphasis in Europe on sustainable agriculture and extensification is likely to lead to an increase in vector tick populations with increased risk of infection. Despite the veterinary and zoonotic importance of this parasite, relatively little research has been carried out on B. divergens, and many questions regarding the parasite's epidemiology and the host's response remain unanswered. A better understanding of the species' biology and host-parasite interactions may lead to improved control mechanisms and new trends in vaccine and antibabesial drug development. This review provides the first comprehensive summary of B. divergens biology, including its morphology, life cycle, and host specificity, and the current state of knowledge of both human and bovine infections.

Molecular studies on Babesia, Theileria and Hepatozoon in southern Europe. Part II. Phylogenetic analysis and evolutionary history

Following a study on molecular epizootiology of Hepatozoon canis and piroplasmids (Babesia spp. and Theileria spp.) in southern Europe, newly obtained sequences of 18s rRNA gene were used for phylogenetic analysis. Partial sequences were analysed in isolates showing high degree of homology (>99%) with previous GenBank entries: H. canis, B. canis vogeli, B. equi (two isolates, Spain1 and Spain2), T. annulata and Theileria sp. The complete gene sequences were used for B. ovis and B. bovis, that showed lower homology (<95%) with rapport to previously reported species or isolates. A first set of phylogenetic trees constructed with partial 18s rRNA sequences showed that most European isolates clustered unambiguously with previously described species, so that minor sequence dissimilarities found are due probably to strain variations. The second set of phylogenetic trees was made using the complete 18s rRNA sequences of 44 species from GenBank and the newly sequenced B. ovis and B. bovis. The analysis revealed for the first time a division of piroplasmids in five clades: (1) B. microti group, with B. rodhaini, B. felis, B. leo, B. microti and T. annae (proposed name for the group, without taxonomic value: Archaeopiroplasmids), (2) Western USA Theilerid-like group (proposed name: Prototheilerids), (3) Theileria group, containing all Theileria species from Bovinae (proposed name: Theilerids), (4) A first group of Babesia species including B. canis and B. gibsoni from canids together with B. divergens and B. odocoilei (proposed name: Babesids), (5) A second group composed mainly by Babesia species from ungulates: B. caballi, B. bigemina, B. ovis, B. bovis and Babesia sp. from cow (proposed name: Ungulibabesids). The bootstrap support obtained with several analytical procedures for this new dicotomy of Babesiidae was always very high. Taking into account the present phylogenetic analysis and additional paleogeographic, parasitological and zoological evidences, two hypothesis on the origin and evolution of piroplasmids groups are presented.

Protectants used in the cryopreservation of microorganisms

The cryoprotective additives (CPAs) used in the frozen storage of microorganisms (viruses, bacteria, fungi, algae, and protozoa) include a variety of simple and more complex chemical compounds, but only a few of them have been used widely and with satisfactory results: these include dimethylsulfoxide (Me2SO), glycerol, blood serum or serum albumin, skimmed milk, peptone, yeast extract, saccharose, glucose, methanol, polyvinylpyrrolidone (PVP), sorbitol, and malt extract. Pairwise comparisons of the cryoprotective activity of the more common CPAs used in cryomicrobiology, based on published experimental reports, indicate that the most successful CPAs have been Me2SO, methanol, ethylene glycol, propylene glycol, and serum or serum albumin, while glycerol, polyethylene glycol, PVP, and sucrose are less successful, and other sugars, dextran, hydroxyethyl starch, sorbitol, and milk are the least effective. However, diols (as well as some other CPAs) are toxic for many microbes. Me2SO might be regarded as the most universally useful CPA, although certain other CPAs can sometimes yield better recoveries with particular organisms. The best CPA, or combination of CPAs, and the optimum concentration for a particular cryosensitive microorganism has to be determined empirically. This review aims to provide a summary of the main experimental findings with a wide range of additives and organisms. A brief discussion of mechanisms of CPA action is also included.