Publisher Summary The piroplasms are protozoa that are highly pathogenic to cattle, sheep, goats, and occasionally even to man. They comprise two genera—namely, Theileria and Babesia . The diseases they induce, known collectively as “theilerioses” and “babesioses,” cause fevers and lead to important economic losses in the tropics, subtropics, and southern Europe. This chapter highlights the differences between the life cycles of Babesia and Theileria species with respect to their morphology, studied by means of light and electron microscopy. The chapter describes the life cycle of piroplasms. They have a typical sporozoan life cycle comprising three phases: (1) Schizogony, an asexual reproduction phase in the vertebrate host. (2) Gumogony, the formation and fusion of gametes inside the intestinal cells of ixodid ticks. (3) Sporogony, an asexual reproduction in the salivary gland of the tick leading to the infectious, saliva-transmitted sporozoites. Comparative biological and morphological studies show that the economically important piroplasms comprise three groups: (1) Babesia species sensu strictu ; (2) Bubesia equi , B. microti ; and (3) Theileria species.

The piroplasms: life cycle and sexual stages.

Publisher Summary Argasid ticks feed rapidly and pass through numerous moults to reach the engorged female stage On the other hand, the feeding of ixodid ticks is characterized by the capacity of each instar to ingest large volumes of host blood and so avoid the frequent host-finding associated with argasids These concentrate their meal with the coxal organ but ixodid ticks eliminate most excess water via the salivary glands, which have the capacity to secrete large volumes of water, particularly during the later stages of feeding This chapter discusses various aspects of the host response that affect tick feeding directly It also studies the dependence on tick salivary glands of the disease-causing organisms Theileria and Babesia for their development and transmission In many species, the salivary glands secrete cement that attaches the tick to the host for several days They synthesize and release a variety of enzymes and other chemicals, which may assist in the development of a feeding lesion and provide an ample flow of blood for engorgement In concentrating the blood meal, the salivary glands not only secrete excess water but also maintain the ionic balance of the hemolymph by selective secretion and retention of ions

Role of Tick Salivary Glands in Feeding and Disease Transmission

Sections of salivary glands from the tick R. appendiculatus have been studied to obtain data on the incidence and development of Theileria parva during feeding. Adult ticks previously fed as nymphs on infected cattle were allowed to attach to rabbits after different periods following moulting and removed for dissection after different periods of attachment. The maximum number of parasites was present from the 3rd to the 5th days of attachment when 30·5–42 % of salivary glands were infected. A small number of undeveloped parasites was observed in the salivary glands of unfed ticks. The parasites were classified by their appearance into young, intermediate and mature forms and it was shown that the greatest numbers of mature forms were present on the 4th and 5th days of attachment. It was concluded that with this strain of ticks, reared and infected under the described conditions, the most suitable time for the recovery of the infective forms of T. parva would be the 4th day of feeding. Acknowledgements are due to the technical staff who contributed to this work, but especially to Mrs D. Backhurst who supervised the processing of the many sections, to Mr B. Wood who prepared the photomicrographs and to Mr K. P. Bailey who maintained the colony of infected R. appendiculatus . This work was carried out during the assignment of one of us (L.P.J.) by the Food and Agricultural Organization of the United Nations to the East African Veterinary Research Organization.

The development of Theileria parva in the salivary glands of the tick, Rhipicephalus appendiculatus.

Theileria parya: Kinetics of replication

There have been few studies specifically on the epidemiology of theileriosis in East Africa. The classical studies of Yeoman (1966a,b; 1967) and McCulloch et al (1968a,b) investigated the cause of the large epidemics of East Coast fever (E.C.F.) which occurred in Sukumal& Tanzania, concentrating on the populations of the tick vector Rhipicephalus appendiculatus. Barnett (1968, 1977) and Barnett & Bailey (1955) reported studies in the field and laboratory which threw considerable light on the epidemiology of Theileria parva in endemic areas of Kenya. FAO (1975) undertook an enormous survey of the tick populations and T. parva antibodies from cattle in Kenya.

S.F. Barnett

Papers

Cyclic development and longevity of theileria parva in the tick rhipicephalus appendiculatus.

Studies on Macroschizonts of Theileria parva