Observations on Theileria parva, the Parasite of East Coast Fever of Cattle

Although a good deal has been written about East Coast Fever in cattle, the literature relating thereto contains very little direct information regarding the parasite which stands in causal relation to the disease. Robert Koch (1898), who was the first to observe the parasite in cases of East Coast Fever occurring in German East Africa, regarded it as but a variety of Piroplasma bovis (= bigeminum) and described the disease as Texas Fever. Theiler (1904) was the first to distinguish clearly East Coast Fever from Redwater. He stated that “the disease has nothing to do with Texas Fever or Redwater; it is a new disease due to a parasite different to the one found in Texas Fever.” Koch (1903—1904), who gave the disease its distinctive name, reached the same conclusions as Theiler. The investigations of Theiler (1904) established the following facts: Cattle which are immune to Redwater are susceptible to East Coast Fever. East Coast Fever is not communicable by blood inoculations (30 experiments, wherein 5 to 2000 c.c. of East Coast Fever blood were inoculated). He noted the absence of haemoglobinuria in the majority of animals affected with East Coast Fever, its presence in the majority of the animals affected with Redwater. He found that in most cases of East Coast Fever, there was no appreciable decrease in the number of red blood corpuscles, this being in marked contrast to what is observed in Redwater. Theiler noted that cattle might harbour both the parasites of Redwater (P. bovis) and those of East Coast Fever (bacillary forms = T. parva). The former generally appeared in the blood “only towards the end of the fever reaction in East Coast Fever,” being previously latent in the animals which had been “salted” against Redwater. He distinguished “two groups of piroplasmosis,” the inoculable (Redwater, canine and equine piroplasmosis) and the uninoculable (East Coast Fever) by injection of infected blood. The parasites in the latter are much smaller than in the former. He named the parasites of East Coast Fever Piroplasma parvum. Theiler distinguished the parasite of East Coast Fever from P. bovis because of the frequent occurrence of bacillary forms and the minute size of the parasite, but he nevertheless retained the new parasite in the genus Piroplasma.

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An experimental study of east coast fever in uganda III. A study of the East Coast fever reactions produced when infected ticks 31 days old are fed on susceptible calves in limited numbers over a period of 3 weeks

Parasitology ◽

10.1017/s0031182000016541 ◽

1951 ◽

Vol 41 (1-2) ◽

pp. 23-35 ◽

Cited By ~ 2

Author(s):

S. G. Wilson

Keyword(s):

East Coast ◽

East Coast Fever ◽

The Other ◽

Theileria Parva ◽

Infected Tick ◽

Control Calf ◽

Group A ◽

Group B ◽

Fever Reaction ◽

Minimum Intensity

In natural grazing grounds, bovines affected with East Coast fever remain ambulatory until a few days or even a few hours before death, and larval and nymphal Rhipicephalus appendwulatus and R. evertsi, which have fed and engorged, will infest the pasture over a wide area. Subsequently, when susceptible cattle graze over this area small numbers of infected instars may attach at intervals and begin to feed. In this experiment an attempt was made to simulate these conditions as closely as possible.In group A wnere one infected tick was fed on the 1st day, two on the 3rd day, and three on the 21st day, two out of six calves developed an unmistakable East Coast fever infection, with Koch's bodies present in gland smears. In one calf (no. 5724) the reaction was most severe and was undoubtedly due to the three ticks which attached on the 1st and 3rd days, while in another calf (no. 115) the reaction was less severe and was most probably due to the three ticks which attached on the 21st day.In group B where one infected tick was fed on the 1st day, two on the 5th day, and three on the 21st day; five out of six calves gave a definite unmistakable East Coast fever reaction with Koch's bodies present in gland smears, four of the reactions being undoubtedly due to the three ticks which attached on the 1st and 5th days. There is as yet no reasonable explanation as to why the number of definite reactors should differ so markedly in the two groups.It is noteworthy that all these reactions were mild and that recovery in each case was uneventful. The only death to occur was control calf no 5729, on which ten infected ticks had fed at one time, but from the results of the other controls it may be assumed that the strain of Theileria parva had by some means become attenuated or that the calves had increased tolerance or resistance.It is difficult to understand why calf no. 109 failed to react in the first experiment but showed some susceptibility when challenged 96 days later, and why calves nos. 5711, 116, 5642 and 39 gave doubtful reactions. No explanation can be given at this stage, but it raises two practical questions. First, it is difficult to assess the minimum intensity of a reaction which is sufficient to give a durable immunity. The fact that calf no. 114, after what appeared to be a definite T. parva reaction, reacted a second time on exposure to infection 110 days later, proved that the immunity was not prolonged. It is true that the first reaction was only mild, but practically the same remarks could be applied to calves nos. 117 and 5725, yet these calves had not lost their immunity on challenge. Secondly, it is difficult to ensure, by observation of daily temperatures alone, that all calves are really fully susceptible before being used on a critical East Coast fever experiment, for if only a few infected ticks are accidentally introduced into stables or grazing paddocks, it may be assumed that mild subclinical infections will result. These calves may then show varying degrees of resistance to subsequent infections, and results such as those experienced in these experiments would be a normal sequelae.The intensity of the leucopaenia appeared to bear no relationship to the number of days Koch's bodies were present in gland smears. It was present before the first rise in temperature in all the calves except no. 114, the only calf to show a second reaction on challenge.

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An experimental study of East Coast fever in Uganda IV. A study of the East Coast fever reactions produced when infected ticks 171 days old were fed on susceptible calves in limited numbers over a period of 3 weeks

Parasitology ◽

10.1017/s0031182000016553 ◽

1951 ◽

Vol 41 (1-2) ◽

pp. 36-45

Author(s):

S. G. Wilson

Keyword(s):

East Coast ◽

Durable Resistance ◽

East Coast Fever ◽

Veterinary Services ◽

Subsequent Infection ◽

Marked Contrast ◽

Fatal Reaction ◽

Group A ◽

Group B ◽

Fever Reaction

This experiment showed that infections of Theileria parva were still viable in nymphae of Rhipicephalus appendictdatus 171 days old, but when nine nymphae were fed on calves at intervals over 22 days the reactions produced were most irregular.In group A reactions varied from acute fatal type to mild, doubtful or no obvious reaction. None of the four animals which survived was protected from subsequent infection when grazed in a tick-infested paddock (Table 1). The two fatal reactions which developed in this paddock varied in intensity; calf no. 5717 showing a typical acute East Coast fever reaction, but the reaction of calf no. 167 showed several atypical features especially in the sporadic appearance of Koch's bodies.In group B the reactions were again in marked contrast to those seen in group A, one fatal reaction developed and only mild transient reactions without the production of Koch's bodies were seen in the remaining five calves. These mild reactions, however, appeared to be sufficient to protect against subsequent re-infection in the tick-paddock (Table 4).It is doubtful if the transient reactions seen in calves nos. 5734 (on the 12th day), 172 and 168 could be diagnosed clinically under field conditions, and further investigations as to the infectivity of these types of reactions are required.In calves nos. 165 and 167 Koch's bodies were absent from all tissue smears at time of death, and diagnosis of the true cause of death by smears alone would therefore be difficult. Reactions such as those given by calves 133 and 139 cast further doubt on the ability to diagnose East Coast fever by gland-smear technique.In general, the results of this experiment appear to indicate that if the original reaction is mild a second reaction may develop within a few weeks with or without the production of Koch's bodies. The development of a durable resistance to further attacks may not, therefore, depend on the presence of Koch's bodies in the peripheral glandular tissues in detectable numbers.My thanks are due to the Director of Veterinary Services, Uganda, for his permission to carry out this work and to publish this paper.

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Theileria parva, the Parasite of East Coast Fever in Cattle

Parasitology ◽

10.1017/s0031182000001980 ◽

1910 ◽

Vol 3 (2) ◽

pp. 117-129 ◽

Cited By ~ 2

Author(s):

George H. F. Nuttall ◽

H. B. Fantham

Keyword(s):

Peripheral Blood ◽

East Coast ◽

East Coast Fever ◽

Theileria Parva ◽

The Subject

In an earlier paper (Nuttall, Fantham and Porter, 1909, Parasitology vol II. pp. 325—340), we recorded our observations on living Theileria parva as seen in the peripheral blood of two cows which succumbed to East Coast Fever1. We now propose to describe our studies upon the parasite in stained preparations made from the animals' blood during the course of the disease and from their organs shortly after death. We shall confine our attention to the types of parasites encountered within red blood corpuscles or to corresponding types which may be occasionally encountered free in the plasma. The subject of “Koch's blue bodies” will receive attention at a later date.

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