Tick-borne Fever Research Articles

Infectious abortion in sheep

WHILE many organisms can cause sporadic, fatal infections of the ovine fetus, a smaller number have a particular ability to colonise the conceptus and cause characteristic syndromes of abortion. The...

Lymphocyte responses to mitogens and rickettsial antigens in sheep experimentally infected with Ehrlichia (Cytoecetes) phagocytophila

Infection of sheep with Ehrlichia (Cytoecetes) phagocytophila, the causative agent of tick-borne fever (TBF), was characterised by a significant reduction in lymphocyte reactivity to the mitogens phytohaemagglutinin, concanavalin A, pokeweed mitogen and Escherichia coli lipopolysaccharide during the period of rickettsiaemia. The addition of the prostaglandin inhibitor, indomethacin, or the nitric oxide inhibitor, N G-monomethyl- l-arginine, had no significant effect on the suppressive effects of E. phagocytophila on lymphocyte reactivity to the mitogens. However, peripheral blood lymphocytes obtained from primed sheep proliferated in the presence of live or heat-inactivated E. phagocytophila. Antigen-specific proliferation was detected in lymphocytes samples obtained 11 to 21 days post-inoculation with E. phagocytophila.

Inhibition of Phagosome-lysosome Fusion in Ovine Polymorphonuclear Leucocytes byEhrlichia (Cytoecetes) phagocytophila

Ehrlichia (Cytoecetes) phagocytophila, the causative agent of tick-borne fever, is an intracellular bacterium that survives and multiplies within granulocytes and monocytes. In the present study, the possible fusion of lysosomes with phagosomes containingE. phagocytophilawas investigated in poly-morphonuclear (PMN) cells of sheep infected with the agent, acid phosphatase cytochemistry and cationized ferritin being used as markers of primary and secondary lysosomal enzymes. Latex beads orCandida albicanswere incubated with infected and uninfected PMN cells and labelled with the same lysosomal markers. Lysosomal enzymes labelled with the markers were commonly found in phagosomes containing latex beads orC. albicans, but there was no evidence of phagosome-lysosome (P-L) fusion in phagosomes containingE. phagocytophila. It was significant that in cells that containedE. phagocytophila, latex beads andC. albicans, P-L fusion occurred only in phagosomes containing latex beads orC. albicans. However, evidence of P-L fusion with phagosomes containingE. phagocytophilawas obtained when PMN cells were incubated with oxytetracycline, which is known to inhibit synthesis of bacterial proteins.These findings indicate thatE. phagocytophilais capable of inhibiting P-L fusion and that oxytetracycline depresses this capability.

Differential haematological effects of tick-borne fever in sheep and goats.

Tick-borne fever (TBF) is a rickettsial disease of domestic and wild ruminants in temperate climates. It is characterized by high fever and severe leukopenia. In the present study, the possible difference in the severity of disease in sheep and goats was investigated by inoculating one group of eight goats and one group of eight sheep with the Old Sourhope (OS) strain of Ehrlichia (Cytoecetes) phagocytophila. All sheep and goats experimentally infected with E. phagocytophila reacted with fever and rickettsiaemia, but there were significant differences between goats and sheep in the severity of clinical disease, the duration and magnitude of fever, the magnitude of rickettsiaemia and the patterns of reduction in the number of total leucocytes. Sheep reacted with fever significantly earlier than goats and the febrile period lasted for a significantly longer period. In contrast, the magnitude of rickettsiaemia was significantly higher in goats than in sheep. Infection with TBF was characterized by a transient increase in the number of neutrophils, which was quickly followed by an acute reduction in the number of lymphocytes and a prolonged reduction in the number of neutrophils in both sheep and goats. In both groups of animals, infection with TBF was also characterized by significant reductions in the total number of red blood cells (RBCs), thrombocytes and packed cell volume (PCV) and the concentration of haemoglobin (Hb). However, the mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) were significantly increased in sheep only.

The effects of Ehrlichia (Cytoecetes) phagocytophila on the clinical chemistry of sheep and goats.

Tick-borne fever (TBF) is a rickettsial disease of domestic and wild ruminants in temperate climates where the hard tick Ixodes ricinus is present. The disease is characterized by a high temperature and severe leukopenia. In the present study, the effects of TBF on the activity of serum alkaline phosphatase (ALP), and on the concentrations of plasma zinc, iron, total bilirubin, urea, creatinine and albumin were investigated by inoculating one group of eight sheep and one group of eight goats with the Old Sourhope (OS) strain of Ehrlichia (Cytoecetes) phagocytophila. All goats and sheep experimentally infected with E. phagocytophila reacted with fever, rickettsiaemia and leukopenia. The leukopenia was due to an acute lymphocytopenia and prolonged neutropenia. In both groups of animals. TBF was characterized by significant reductions in the activities of serum ALP and concentrations of plasma zinc, iron and albumin. However, there were significant increases in the concentrations of plasma total bilirubin, urea and creatinine in both species of animals. The reductions in ALP and iron were significantly more pronounced in sheep than in goats.

Detection of Ehrlichia phagocytophila DNA in Ixodes ricinus ticks from areas in Switzerland where tick-borne fever is endemic.

A total of 1,523 adult Ixodes ricinus ticks were collected from regions where bovine ehrlichiosis is endemic and were examined for Ehrlichia phagocytophila via PCR. Of the ticks from cattle with ehrlichiosis, the ticks from healthy cattle, and the free-living ticks, 26.5% (18 of 68), 4.4% (35 of 802), and 0.8% (5 of 653), respectively, were positive.

Natural prevalence of infection with Ehrlichia ( Cytoecetes) phagocytophila of Ixodes ricinus ticks in Scotland

Ixodes ricinus nymphs and adults were collected from vegetation and from sheep at four sites in Scotland typical of areas endemic for tick-borne fever in sheep caused by infection with Ehrlichia ( Cytoecetes) phagocytophila (Rickettsiales). The great majority of ticks examined was from woodland sites adjacent to sheep farms where there was a high probability of them feeding on roe deer ( Capreolus capreolus) in a non-domestic focus of infestation and infection. Ticks were examined for infection by five methods. Batches of ticks were examined either by feeding on susceptible sheep or by feeding on rabbits and then prepared as stabilate which was inoculated into susceptible sheep. The sheep were monitored for clinical signs of tick borne fever. Batches of ticks were examined by polymerase chain reaction for Ehrlichia phagocytophila. Salivary glands were dissected out and stained by the Feulgen method to detect Ehrlichia masses, and were examined by indirect fluorescent antibody test. Each of the methods detected infection in ticks and the prevalence of infection in nymphs with the various methods ranged from >0.25% to 2.0%. Small samples of adults examined by Feulgen staining of salivary glands indicated infection prevalences of 2.1% in males and 1.6% in females. It is considered that these low infection prevalences may be typical of natural foci of infection where deer could be a major host of ticks and E. phagocytophila.

Serological, hematologic, and PCR studies of cattle in an area of Switzerland in which tick-borne fever (caused by Ehrlichia phagocytophila) is endemic.

The purpose of this study was to examine the seasonal variations in seroprevalence to Ehrlichia phagocytophila in cattle pastured during the summer months in an area where tick-borne fever is endemic. The study was performed during a 1-year period from April 1996 to March 1997 and involved 34 cows, 22 pregnant heifers, and 14 calves. Blood samples, collected from all 70 cattle once a month, were used to determine serum immunoglobulin G titers by indirect immunofluorescence. In addition, blood smears were examined for Ehrlichia organisms, and PCR amplification was performed for the molecular detection of E. phagocytophila. Prior to the pasture period, the seroprevalence was 16%. Two weeks after the start of pasturing, it was 43%, after which it progressively increased and reached a maximum of 63% in September. The seroprevalence progressively decreased after the end of pasturing to a low of 23%. The variation in antibody titers was similar to that of seroprevalence. E. phagocytophila organisms were detected in blood smears of 7 animals and by nested PCR in 12. Only four cows, which were on the pastures of endemicity for the first time, had clinical signs of ehrlichiosis. This study demonstrated marked seasonal variations in seroprevalence and in serum titers of antibody to E. phagocytophila in cattle. The incidence of clinical signs of ehrlichiosis was increased in cattle grazing on the pastures of endemicity for the first time.

Ehrlichial DNA amplified from Ixodes ricinus (Acari: Ixodidae) in France.

Granulocytic ehrlichia 16S rDNA was amplified for the 1st time from an Ixodes ricinus (Linne) tick collected in Europe. Sequence analysis of polymerase chain reaction products from the 16S rRNA gene demonstrated the organism from which it originated to be closely related to the agent of human granulocytic ehrlichiosis, an emerging disease that was recently described in the United States; Ehrlichia phagocytophila, the agent of tick-borne fever of ruminants in Europe; and Ehrlichia equi. the agent of the worldwide equine granulocytic ehrlichiosis. These granulocytic ehrlichiae have been associated with Ixodes spp. ticks that may act as vectors. It remains to be determined if each of these granulocytic ehrlichiae, that may constitute variants of the same species, is responsible for a specific disease in animals and in humans.

Intrauterine infection with Ehrlichia phagocytophila in a cow

An infection with Ehrlichia phagocytophila, the agent of tickborne fever, can cause abortion or stillbirth in cows in late pregnancy but, to the authors' knowledge, there have been no reports...

Clinical findings in cows after experimental infection with Ehrlichia phagocytophila.

The goal of this study was to determine the clinical signs and course of disease in five lactating cows and in five dry cows after experimental infection with Ehrlichia phagocytophila. Ten clinically healthy Swiss Braunvieh cows, seronegative for E. phagocytophila, were injected with 50 ml of whole blood containing E. phagocytophila. The cows were examined daily for 21 days, and blood samples were collected for microscopic examination of leukocytes for the infective agent. All cows became ill with symptoms of tick-borne fever after an incubation period of 5 to 9 days. The most important clinical signs were pyrexia (40.2-41.7 degrees C), decreased milk production and mildly to moderately disturbed general condition. In addition, there were respiratory symptoms such as polypnea, nasal discharge, cough and abnormal lung sounds. Clinical signs returned to normal in all cows without treatment after an average of 8 days. E. phagocytophila bodies were seen in leukocytes 5-8 days after infection and were present for 6-14 days. The course of disease was more severe in dry cows than in lactating cows. It can be concluded that experimental infection of cows with E. phagocytophila generally has a mild course. However, the associated decrease in milk production may be of economic importance.

Microbiological research at the Centre for Tropical Veterinary Medicine (CTVM).

The nature of the research carried out by the staff of the Microbiology Section of the Centre for Tropical Veterinary Medicine (CTVM) at home and abroad is illustrated by precis of projects on rinderpest, orf in goats and sheep, bovine dermatophilosis, contagious caprine pleuropneumonia, tick-borne fever in goats and sheep, bovine petechial fever, and caprine cowdriosis.

Equine piroplasmosis

Equine Veterinary EducationVolume 8, Issue 1 p. 33-36 Equine piroplasmosis L. P. Phipps, L. P. Phipps Parasitology Department, Central Veterinary Laboratory, New Haw, Weybridge, Surrey KT15 3NB, UK Biographical details: : Manager of Immunodiagnostic Unit of Parasitology Department at CVL. Has 18 years experience in the field of tick borne diseases with particular interest in equine and bovine babesiosis, Dourine in horses and Tick Borne Fever (C. phagocytophila) of cattle and sheep.Search for more papers by this author L. P. Phipps, L. P. Phipps Parasitology Department, Central Veterinary Laboratory, New Haw, Weybridge, Surrey KT15 3NB, UK Biographical details: : Manager of Immunodiagnostic Unit of Parasitology Department at CVL. Has 18 years experience in the field of tick borne diseases with particular interest in equine and bovine babesiosis, Dourine in horses and Tick Borne Fever (C. phagocytophila) of cattle and sheep.Search for more papers by this author First published: February 1996 https://doi.org/10.1111/j.2042-3292.1996.tb01647.xCitations: 9 AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume8, Issue1February 1996Pages 33-36 RelatedInformation

徳之島におけるマダニ類と紅斑熱群リケッチアの調査

徳之島におけるマダニ類と紅斑熱群リケッチアの調査

Sequential pathology of tick-borne fever

The sequential pathology and clinical responses of 12 sheep infected with the Sourhope strain of Cytoecetes phagocytophila are described. During the experimental period of 3 weeks, the clinical effects were mild, as is usual. There was transient leucopenia, affecting mainly lymphocytes, eosinophils and neutrophils. Parasitaemia was detected from days 5 to 16, approximately. A mild but consistent histopathological response up to day 21 comprised (i) pulmonary alveolitis with minimal shedding of cells, (ii) follicular and especially parafollicular lymphoreticular reactions in lymph nodes and spleen, (iii) mesangial glomerulitis, and (iv) in the cranial nervous system marked choroiditis but minimal reaction in the brain. Two forms of intracytoplasmic inclusions were found, a smaller, granular basophilic structure occurring in clumps and an intravacuolar pleomorphic form. In tissue sections they were mainly associated with lymphoid and macrophagic cells. The significance of these findings is discussed including the problems of differential diagnosis in complex infections.

Parasite control in transhumant situations

Transhumance is defined as ‘seasonal moving of livestock to regions of different climate’. It is an integral part of livestock production in many parts of the world and takes several forms including moving of livestock from lowland to mountainous pastures or from dry to humid areas. The impact of transhumance on parasite populations of livestock and on parasite control is described, mainly using examples from Europe. The epidemiology of trichostrongylidosis of cattle, mainly caused by Ostertagia ostertagi and Cooperia oncophora, is characterised by prolonged survival of overwintered infective larvae until the end of June. Cattle moved to such contaminated pastures in a transhumant grazing system are exposed to these larvae and may be protected, during the second half of the grazing season until autumn, by a late application (June/July) of an intraruminal drug-release device. Community pastures used in a transhumant system with mixed grazing of young cattle originating from various farms may enhance transmission of dictyocaulosis. Therefore, specific prophylactic measures are required. Hill sheep nematode populations may differ from those in lowland sheep in the Haemonchus contortus generally plays a minor role in hill sheep in which Ostertagia circumcincta and Nematodirus spp. predominate. Infections with Fasciola hepatica and Dicrocoelium dendriticum can be acquired on mountainous pastures by cattle, sheep and other livestock grazing in a transhumant system as intermediate hosts of these parasites may find suitable habitats in these regions. There is evidence that in the prealpine and alpine area both parasites are mainly transmitted in two-season cycles. Further examples for the impact of transhumance on parasite-host inter-relationships include cysticercosis in cattle, echinococcosis, psoroptic mange in sheep, tick-borne fever of cattle, and hypodermosis in cattle. These are described and discussed.

Immunosuppression in sheep experimentally infected with Ehrlichia phagocytophila

The effect of tick-borne fever (TBF) on antibody formation and lymphocyte proliferation in sheep was studied following experimental infection with Ehrlichia phagocytophila. All infected sheep developed fever within three to four days. The sheep recovered clinically within eight days. Both infected and non-infected control sheep were immunised twice with different antigens, that is, on days 9 and 35 following the experimental infection. The levels of antibodies produced against tetanus toxoid and influenza virus in the infected sheep were significantly lower than in the control animals. The findings indicated that a TBF-infection may impair both primary and secondary antibody responses for up to six weeks. Immunisation with Actinomyces pyogenes resulted in significantly higher antibody titres in the TBF-infected group than in the control group, as measured by an enzyme-linked immunosorbent assay ( ELISA). It is believed that TBF-induced neutropenia may lead to increased exposure to A pyogenes-antigens and thereby enhance antibody production. Antibodies to E phagocytophila were measured by the indirect fluorescent antibody test and by an ELISA. The inoculated sheep responded with the formation of antibodies to E phagocytophila at one week (P<0·025), and showed a peak response at four weeks (P<0·0005) after inoculation. The antibody titre decreased between four and six weeks, but was still high at six weeks (P<0·0005). The lymphocyte responses to phytohaemagglutinin (PHA) concanavalin A (Con A) and pokeweed mitogen (PWM) were lower than in the control group and this difference was significant at most time points after infection. The lower responses to Con A and PWM were demonstrated within six weeks after the inoculation, whereas the lower response to PHA was shown within four weeks. Serum from one sheep, collected four weeks after infection, suppressed the in vitro lymphocyte response to Con A strongly, and the response to PHA and PWM moderately. This indicates that unidentified serum factors may at least be partly responsible for the suppressed mitogen responses.

Tick-borne fever as a possible predisposing factor in septicaemic pasteurellosis in lambs.

Tick-borne fever as a possible predisposing factor in septicaemic pasteurellosis in lambs.

The effects of tick-borne fever on the susceptibility of ovine polymorphonuclear cells to P. haemolytica Cytotoxin

Tick-borne fever predisposes sheep to secondary infections by Pasteurella haemolytica. Polymorphonuclear (PMN) cells obtained from sheep 2 to 7 days after the onset of parasitaemia due to Cytoecetes phagocytophila, the causative agent of tick-borne fever, were significantly more susceptible in vitro to the cytotoxin of P. haemolytica than PMN obtained from age-matched control sheep.

Tick-Borne Fever in Lambs of Different Ages

Four groups of lambs aged 1 week, 4 weeks, 1/2 year and 1 year old respectively were inoculated with Ehrlichia phagocytophila infected blood. Clinical signs, temperature reactions, haematological changes and parasitaemia were more moderate in lambs inoculated with E. phagocytophila at the age of 1 week than those recorded in the older animals. The clinical response to tick-borne fever (TBF) appears to be more severe with increasing age of the lambs. The lymphocyte reactivity to mitogens was reduced in the TBF infected lambs, and was most pronounced in lambs in the 3 older age groups.