Transmission of Theileria parva by a population of Rhipicephalus appendiculatus under simulated natural conditions

Parasitology ◽  
1983 ◽  
Vol 86 (2) ◽  
pp. 255-267 ◽  
Author(s):  
A. S. Young ◽  
B. L. Leitch ◽  
T. T. Dolan ◽  
R. M. Newson ◽  
P. N. Ngumi ◽  
...  
Keyword(s):  
Salivary Gland ◽  
Salivary Glands ◽  
Cold Season ◽  
Rhipicephalus Appendiculatus ◽  
Theileria Parva ◽  
Infected Tick ◽  
Lethal Challenge ◽  
Lethal Infection ◽  
Sexual Stages ◽  
High Parasitaemias

SUMMARYA 2 hectare paddock on the Muguga Estate, Kiambu District of Kenya (altitude 2100 m) free of Theileria parva-iniected ticks was seeded by applying Rhipicephalus appendiculatus nymphs to cattle infected with Theileria parva (Kiambu 4). It was estimated that over 50000 engorged nymphs fell onto the pasture from 4 cattle with high parasitaemias during the cold season (June). Samples of these ticks were placed in plastic cylinders under the vegetation in the paddock and sexual stages of T. parva were detected in gut lumen smears in these samples up to 21 days alter repletion. Zygotes were first observed to transform into kinetes on day 55 and parasites were first detected in salivary glands of adults on day 64. Moulting of the nymphs started on day 60 after repletion and was completed by day 87. Cattle introduced into the paddock showed their first infestation with adult R. appendiculatus on day 64 after repletion of the nymphs and the infestation level gradually increased. On day 76 after repletion, 17% of a sample of adult ticks infesting cattle showed salivary gland infections with T. parva and this increased to over 70% by day 150. From day 360 onwards, a decrease in both the percentage of ticks infected and the number of salivary gland acini infected/tick was noted. In addition, T. parva infections within the salivary glands required a longer period of feeding in the older ticks before they developed into sporozoites. Cycling of Theileria through ticks was prevented by the removal of female ticks before they completed repletion. Lethal challenge levels of T. parva for cattle existed in the paddock up to day 547 after repletion, after which introduced cattle showed no infection or only a sub-lethal infection. Cattle introduced into the paddock on day 808 after repletion showed no evidence of T. parva infection. The tick infestation of introduced cattle decreased markedly from day 368 and infestation had virtually ceased by day 808

The effect of irradiation on the susceptibility of Rhipicephalus appendiculatus ticks to Theileria parva infection

Parasitology ◽  
1981 ◽  
Vol 82 (3) ◽  
pp. 473-479 ◽  
Author(s):  
A. S. Young ◽  
B. L. Leitch ◽  
A. D. Irvin ◽  
D. A. E. Dobbelaere
Keyword(s):  
Salivary Gland ◽  
Salivary Glands ◽  
Irradiation Dose ◽  
Subsequent Development ◽  
Rhipicephalus Appendiculatus ◽  
Detectable Effect ◽  
Theileria Parva ◽  
Theileria Parva Infection

SUMMARYIrradiation doses of 800 rad. or less had no detectable effect on the subsequent development of unfed nymphal Rhipicephalus appendiculatus ticks. Doses of 1600 rad. or above impaired feeding and moulting and delayed the subsequent development of unfed nymphs. At 6400 rad. no ticks completed their moult. Unfed nymphal R. appendiculatus irradiated at 0, 400, 800 and 1600 rad. were applied to 3 cattle infected with T. parva (Kiambu 4). The Theileria infections in the salivary glands of the resultant adult ticks were assessed and it was found that irradiation doses of 800 rad. or less had little effect on the Theileria infections, but an–irradiation dose of 1600 rad. greatly reduced the level of infection. The numbers of salivary gland acini in ticks of this group were reduced but the percentage of infected acini was similar.

Estimation of heritability of susceptibility to infection with Theileria parva in the tick Rhipicephalus appendiculatus

Parasitology ◽  
1995 ◽  
Vol 111 (1) ◽  
pp. 31-38 ◽  
Author(s):  
A. S. Young ◽  
T. T. Dolan ◽  
F. N. Mwakima ◽  
H. Ochanda ◽  
S. N. Mwaura ◽  
...  
Keyword(s):  
Salivary Gland ◽  
Rhipicephalus Appendiculatus ◽  
Theileria Parva ◽  
Infected Tick ◽  
Male And Female ◽  
Susceptibility To Infection ◽  
Sib Families ◽  
Heritability Estimates

SUMMARYHeritability of susceptibility to infection with Theileria parva was estimated from full sib families of Rhipicephalus appendiculatus ticks. Male and female ticks of 2 stocks were mated singly. Nineteen full sib families of the Muguga stock and 17 full sib families of the Kiambu stock were obtained. Nymphae of these families were fed on cattle infected with T. parva so that the ticks became replete on days 16 and 17 after infection when the blood was parasitaemic with intraerythrocytic piroplasms. The T. parva infections were assessed in the resultant adult ticks of each full sib group and the abundance of infection, the number of salivary gland acini infected/tick, was found to be the most useful parameter for analysis. Estimates of heritability of the susceptibility to infection with T. parva for the Kiambu and the Muguga tick stocks were 0·24 and 0·26 respectively. Using only the data from ticks which fed on day 16, the heritability estimates were 0·39 for the Kiambu stock and 0·59 for the Muguga stock. These results indicate that tick lines of high or low susceptibility for T. parva infection could be produced through selection.

Factors influencing infections in Rhipicephalus appendiculatus ticks fed on cattle infected with Theileria parva

Parasitology ◽  
1996 ◽  
Vol 113 (3) ◽  
pp. 255-266 ◽  
Author(s):  
A. S. Young ◽  
T. T. Dolan ◽  
S. P. Morzaria ◽  
F. N. Mwakima ◽  
R. A. I. Norval ◽  
...  
Keyword(s):  
Salivary Gland ◽  
Leukocyte Count ◽  
Sampling Period ◽  
Rhipicephalus Appendiculatus ◽  
Type I ◽  
Theileria Parva ◽  
Infected Tick ◽  
Factors Associated ◽  
Tick Infection ◽  
Interactive Modelling

SUMMARYA large database on the transmission of a stabilate of the Theileria parva Muguga stock from one breed of cattle using two stocks of Rhipicephalus appendiculatus, Muguga and Ol Pejeta was developed and analysed. Factors associated with the ticks and cattle, and the infections developing in cattle were studied in relation to the infection variables in the tick batches harvested daily from cattle. Generalized Linear Interactive Modelling (GLIM) was used to determine the importance of factors and interactions in influencing the levels of tick infection variables using Type I and Type III sums of squares analyses. Analysis of the 6 variables, prevalence (percentage of ticks infected), abundance (mean number of infected salivary gland acini per tick examined) and intensity (mean number of infected salivary gland acini per infected tick) in batches of 30 male and 30 female ticks showed that 24 covariates, factors or interactions had a significant effect (P> 0·05). Certain covariates and factors were particularly important for all 6 tick infection variables; parasitaemia of animal on the day of tick harvest, stabilate dilution administered to animal, month in which tick batch was harvested, minimum packed cell volume of animal over the sampling period, age of animal, and the minimum leukocyte count of the animal over the sampling period. The GLIM analyses were found to be a useful tool in identifying factors that influence infection levels and in devising methods of producing tick batches with more predictable infections.

East Coast fever: correlation between the morphology and infectivity of Theileria parva developing in its tick vector

Parasitology ◽  
1973 ◽  
Vol 66 (3) ◽  
pp. 539-544 ◽  
Author(s):  
R.E. Purnell ◽  
C. G. D. Brown ◽  
M. P. Cunningham ◽  
M. J. Burridge ◽  
I. M. Kirimi ◽  
...  
Keyword(s):  
Salivary Glands ◽  
East Coast ◽  
Rhipicephalus Appendiculatus ◽  
East Coast Fever ◽  
Theileria Parva ◽  
Supernatant Fluid ◽  
Tick Vector

Rhipicephalus appendiculatus ticks, infected with Theileria parva, were fed on rabbits and removed at daily intervals for 9 days. Half of the ticks removed were dissected and their salivary glands processed and examined for parasites. The remaining ticks which had been removed were ground up and aliquots of the supernatant fluid thus obtained were injected into East Coast fever susceptible cattle. Cattle injected with supernatant fluids from ticks fed for 4–9 days became infected, and this could be correlated with the histological detection of mature parasites in the corresponding ticks. The most highly infective supernatant fluids were prepared from 5-day-fed ticks. In a second experiment it was shown that female ticks of a variety of weights contained infective particles of T. parva.

Correlation between the morphology and infectivity of Theileria lawrencei developing in the tick Rhipicephalus appendiculatus

Parasitology ◽  
1975 ◽  
Vol 71 (1) ◽  
pp. 27-34 ◽  
Author(s):  
A. S. Young ◽  
R. E. Purnell ◽  
C. D. Kimber ◽  
R. C. Payne
Keyword(s):  
Salivary Glands ◽  
Representative Sample ◽  
Rhipicephalus Appendiculatus ◽  
African Buffalo ◽  
Supernatant Fluid ◽  
Minimal Essential Medium ◽  
Infected Tick

Adult Rhipicephalus appendiculatus ticks, infected as nymphs by feeding them on an African buffalo harbouring Theileria lawrencei, were applied to the ears of rabbits.Equal numbers of the feeding ticks were removed daily from rabbits and either dissected and processed so that parasites in their salivary glands could be examined morphologically and classified, or ground in Eagle's Minimal Essential Medium, to harvest parasites from the ticks in the resultant supernatant fluid. The infectivity of the supernatant fluid was tested by inoculation of aliquots into groups of susceptible cattle.It was found that supernatant fluids produced from day 0 to day 2 fed ticks were uninfective to cattle but those produced from 3 to 9 days were infective. The most infective supernatant fluid was produced from 6 day fed ticks.The reactions resulting in cattle were correlated with the number and morphology of parasites in sections of salivary glands and it was found that mature parasites coincided with infectivity of the supernatant fluid to cattle.From the reactions in cattle inoculated with supernatant fluids from 5 and 6 day fed ticks it was concluded that this method of harvesting parasites was efficient.Examination of the salivary glands of a representative sample of a T. lawrencei infected tick batch is a potential means of screening material for T. lawrencei stabilates.

Differential development and emission ofTheileria parvasporozoites from the salivary gland ofRhipicephalus appendiculatus

Parasitology ◽  
1995 ◽  
Vol 111 (2) ◽  
pp. 153-160 ◽  
Author(s):  
M. K. Shaw ◽  
A. S. Young
Keyword(s):  
Salivary Gland ◽  
Salivary Glands ◽  
Rapid Development ◽  
Secretory Activity ◽  
Rhipicephalus Appendiculatus ◽  
Parasite Development ◽  
Mammalian Host ◽  
Free Access ◽  
Collecting Ducts ◽  
The Individual

SUMMARYThe initiation of feeding of infectedRhipicephalus appendiculatusadults induces the rapid development ofTheileria parvasporoblasts within the salivary gland acini leading to the production of numerous sporozoites which are inoculated into the mammalian host initiating infection. In this study the pattern of development, host cell specificity and emission ofT. parvasporozoites within the salivary glands of heavily infected, 4-day fed adultR. appendiculatusticks was examined. Infected acini were randomly distributed throughout the salivary gland. Sporozoite development within each gland was not synchronized and wide variation in the rate of parasite development, which correlated with the secretory activity of the individual acinus, was observed in all glands examined. Previous studies had shown thatT. parvadeveloped primarily in Type III ‘e’ cells. However, in heavily infected salivary glands sporogony and the emission of mature sporozoites also occurred in ‘c’ cells of Type II acini. Sporozoite emission from infected cells occurred by a process similar to apocrine secretion. The loss of the apical membrane of the infected cell allowed sporozoites free access to the lumen of the acinus and into the collecting ducts of the salivary gland. Sporozoite discharge was gradual since few parasites were found in the acinus valve or in the collecting ducts. Furthermore, the small size of the acinar valve aperature ensures that only small numbers of sporozoites can be released at any one time from an infected acinus.

Genes transcribed in the salivary glands of female Rhipicephalus appendiculatus ticks infected with Theileria parva

2004 ◽  
Vol 34 (10) ◽  
pp. 1117-1128 ◽  
Author(s):  
Vishvanath Nene ◽  
Dan Lee ◽  
Simon Kang’a ◽  
Robert Skilton ◽  
Trushar Shah ◽  
...  
Keyword(s):  
Salivary Glands ◽  
Rhipicephalus Appendiculatus ◽  
Theileria Parva
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