Studies in Tick-borne Fever of Sheep. I. Transmission by the Tick, Ixodes ricinus, with a Description of the Disease Produced

Abstract

1. The causal agent of tick-borne fever is transmitted by the adult female and the nymphal stage of the tick Ixodes ricinus. Two female ticks are sufficient to produce infection in a sheep. The larval stage does not appear to be infective. In a limited number of experiments the disease has not been produced in sheep by the inoculation of emulsions of presumably infective ticks.2. The disease as produced by tick infestation is characterised by a period of incubation which varies from 3 to 13 days, after which there is a sharp rise in temperature; a “plateau” type of febrile reaction follows which lasts from 6 to 22 days, the temperature gradually subsiding to normal. Affected animals usually recover. Mortality as a direct result of infection is rare, but there is evidence to suggest that tick-borne fever may predispose affected animals to death from secondary causes.3. The blood of a sheep which has reacted to the disease remains infective for some time after the subsidence of the thermal reaction.4. The goat is susceptible to tick-borne fever.5. The economic importance of tick-borne fever is discussed.

Dynamic Transmission of NumerousAnaplasma phagocytophilumGenotypes among Lambs in an Infected Sheep Flock in an Area of Anaplasmosis Endemicity

“…However, other nidiculous Ixodes species, which have a far more limited host range, such as Ixodes trianguliceps, have also been proposed and/or demonstrated to be competent vectors (2,3). Although A. phagocytophilum is transstadially maintained in infected ticks, transovarial transmission does not occur (15,20,22); hence, exploitation of mammalian reservoir hosts is essential to its natural persistence.…”

“…Studies over the past few years have revealed that A. phagocytophilum has a wide mammalian host range, with infections being detected in several species of rodents, domesticated and wild-living ruminants, companion animal species, and humans (1,6,13,15,20,25,34). Among these, rodents and ruminants, which are key hosts for vector ticks, are thought to serve central roles in the maintenance of A. phagocytophilum in nature as important reservoir hosts; surveys of populations of species belonging to both groups of animals have revealed that a significant proportion are subclinically infected with the bacterium (1,10,34,35).…”

“…For instance, Ogden and colleagues (21,22) demonstrated the maintenance of A. phagocytophilum in "fell"-grazing sheep flocks in the absence of other important hosts such as rodents or deer. Early studies revealed that A. phagocytophilum infections can persist for several months or longer in sheep (15), and more recent experimental studies have further quantified their dynamics (11,31).…”

Transmission ofAnaplasma phagocytophilumtoIxodes ricinusTicks from Sheep in the Acute and Post-Acute Phases of Infection

“…phagocytophilum is transmitted by ixodid ticks. In the United States the principal vectors are Ixodes scapularis and I. pacificus (35,36), while in Europe the main exophilic tick vector is I. ricinus (22). A. phagocytophilum is transstadially transmitted by these vector ticks, and there is no evidence of transovarial transmission (22,27,29,37).…”

PCR Detection and Serological Evidence of Granulocytic Ehrlichial Infection in Roe Deer ( Capreolus capreolus ) and Chamois ( Rupicapra rupicapra )

“…Transovarial transmission of Ehrlichia species appears to be inefficient in ticks (33), and mammalian hosts are therefore presumed to play an important role in the maintenance and propagation of Ehrlichia species in nature. The white-footed mouse (Peromyscus leucopus), besides being a major host for immature I. scapularis, is apparently a main reservoir host for species of GE.…”