Theilerial parasites isolated from carrier cattle after immunization withTheileria parvaby the infection and treatment method

Abstract

Groups of cattle were immunized with 10(-2) dilutions of sporozoite stabilates of Theileria parva lawrencei derived from African buffaloes either alone or in combination with Theileria parva parva derived from cattle and concomitant treatment with either long or short-acting formulations of oxytetracyline. At 90 or 120 days after infection, uninfected Rhipicephalus appendiculatus nymphal ticks were applied to individual immunized cattle and the resultant adults ticks were applied to individual susceptible cattle. Theilerial infection developed from ticks fed on 6 out of 11 animals investigated for evidence of a carrier state. Two additional animals were shown by cell-culture isolation to have persistent theilerial infections. Nine cattle infected with the parasites from carrier animals were treated with paravaquone and 7 recovered. These recovered cattle were then challenged with the original immunizing stabilates at 10 degrees dilution together with the original immunized and carrier cattle. Six out of 7 cattle which had recovered from carrier-derived infection succumbed to this challenge and died but none of the original immunized cattle showed theilerial reactions. When a carrier-derived sporozoite stabilate was used to challenge cattle immune to the original immunizing parasite, they proved to be immune. Cattle immune to the carrier-derived parasites were all immune to challenge with the original parasite. A monoclonal antibody profile against T. parva schizonts isolated by cell culture from samples of the experimental animals did not appear to be sensitive enough to determine the antigenic differences between the carrier-derived parasite and the original immunizing parasite. Indications are that the carrier state is not likely to produce new antigenic strains which would be dangerous to immunized cattle.

The current status of major tick borne diseases in Zambia

“…Currently immunization by the infection and treatment method using live vaccines based on infective sporozoite stages of the parasites is so far the most prominent method [7,8,28,45,58,[65][66][67][89][90][91]. In this regard, the Katete and Chitongo stocks have successfully been used in the Eastern and Southern Provinces of Zambia, respectively.…”

“…Studies have shown that immunized cattle are protected against challenge provided the appropriate parasite stocks are used [91,112]. It is also known that immunized cattle as well as those that recover naturally from ECF/ CD are carriers of the infection and therefore, can serve as a source of infection for others [22,23,39,45,112]. These vaccines are poorly adopted in the region, mainly because of problems associated with the use of live parasites.…”

Immuno-informatics Analysis to Identify Novel Vaccine Candidates and Design of a Multi-Epitope Based Vaccine Candidate Against Theileria parasites

“…However, this vaccine needs a cold chain for transportation and storage which leads to a huge increase in its cost (approximately $8–12 per dose). Further, some vaccinated cattle, especially immunocompromised cattle, remain as a source of transmission of parasites to other cattle ( 9 ).…”

Rhipicephalus appendiculatus ticks transmit Theileria parva from persistently infected cattle in the absence of detectable parasitemia: implications for East Coast fever epidemiology

“…Despite this, most of what is known about the tick-borne acquisition and transmission of T. parva by R. appendiculatus has been gathered through laboratory studies of cattle undergoing the short-lived acute stage of infection [ 9 – 14 ]. Animals that recover from acute disease can remain persistently infected and serve as reservoirs for R. appendiculatus ticks [ 15 ]. In areas where natural transmission occurs, a phenomenon known as endemic stability has been described as “a climax relationship between host, agent, vector and environment in which all coexist with the virtual absence of clinical disease” [ 1 ].…”