Biomedical subjects

F Jongejan

Publications and source records attributed to F Jongejan.

At least 73 records · Page 4Linked to original sources

PubMed1991

The tick-borne rickettsia Cowdria ruminantium has a Chlamydia-like developmental cycle.

The development of the tick-borne rickettsial pathogen Cowdria ruminantium (S stock) was studied in bovine umbilical endothelial (BUE) cell cultures and in goat choroid plexus, by light- and electron microscopy. Cowdria divided by binary fission within intracytoplasmic vacuoles resulting in large colonies of reticulate bodies. After three to four days in culture, reticulate bodies developed into smaller intermediate bodies characterized by an electron-dense core. Shortly before disruption of the host cells, intermediate bodies condensed further into electron-dense elementary bodies, which were released into the culture medium. Elementary bodies invade other endothelial cells thus initiating a new infectious cycle which lasts between 5 and 6 days. In the infected goat choroid plexus similar reticulate and intermediate bodies were identified within vacuoles of capillary endothelial cells. However, extracellular elementary bodies were not detected. Another stock of Cowdria (W) showed an identical developmental cycle as that of the S stock. The W isolate was also pathogenic for mice, making it possible to test the infectivity of reticulate and elementary bodies in these animals. Reticulate bodies appeared to be less infective than elementary bodies. The developmental cycle of Cowdria resembles the cycle known to occur in Chlamydia. Moreover, Cowdria has other similarities with Chlamydia. It has a Gram-negative envelope, it does not store iodine-stainable carbohydrates and may lack peptidoglycan as does Chlamydia. It is concluded, that Cowdria and Chlamydia are to a certain extent related, confirming a recent report that both organisms have certain antigenic determinants in common. Since Cowdria is also related to Ehrlichia it may well be that Cowdria takes an intermediate position between Chlamydia and Ehrlichia. The phylogenetic relationship between Cowdria and Chlamydia and also with Ehrlichia should be further elucidated by molecular analysis using 16S ribosomal DNA sequences.

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PubMed1991

Lack of cross-protection between Cowdria ruminantium and Ehrlichia phagocytophila.

Antigenically distinct stocks of Cowdria ruminatium from Senegal and South Africa were compared with a Dutch isolate of Ehrlichia phagocytophila in cross-immunity trials in goats. There was a complete absence of cross-immunity between E. phagocytophila and C. ruminantium, despite previous observations that both rickettsial organisms have certain antigenic determinants in common.

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PubMed1990

[Comparison between 3 antigens for the serodiagnosis of heartwater disease by indirect immunofluorescence].

A cell line of bovine endothelial cells (E5), infected with 3 different stocks of Cowdria ruminantium, was used as antigen in an indirect fluorescent antibody test for the serodiagnosis of heartwater. These antigens were compared to peritoneal macrophages from mice infected with the Kümm stock and to caprine neutrophils in primary cultures from goats infected with 4 different stocks of Cowdria. The use of endothelial cell cultures proved to be superior in all respects. The antigens can be produced in large quantities at a low cost, contrary to the other types. The reaction is easily and quickly read, compared to the laborious reading of neutrophil or macrophage antigens which often contain few and small colonies of Cowdria. Moreover, not all stocks are suitable for the preparation of neutrophil antigens, while macrophage antigen can only be obtained with the Kümm stock. Endothelial cell antigens also distinguish serotypes in C. ruminantium, but these differences seem to be less pronounced than those found with neutrophil antigens. Finally, the specificity of endothelial cell antigens appears to be better than that of Kümm antigen and comparable to that of neutrophil antigens. The use of Kümm antigen may have been responsible to a large extent for past unexplained positive serological results on certain Caribbean islands where it has not been possible to isolate Cowdria and where no clinical evidence of the disease has been found.

Animals↗

PubMed1990

[Presence of Theileria annulata in Mauritania].

A fatal case of bovine theileriosis by Theileria annulata is reported from Mauritania in a Friesian cow born in a dairy farm in Nouakchott. The farm was originally established with cattle imported from France. Specific diagnosis was based on piroplasm morphology and on high specific antibody titres in some of the animals. The only tick found in the herd was Hyalomma dromedarii. Four of 49 local zebus sampled at random in the south of the country had high specific antibody titres to T. annulata, while 14 had lower or doubtful titres. The infection therefore appears to be autochthonous.

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PubMed1990

Observations on mouse-infective stocks of Cowdria ruminantium: microscopical demonstration of the Kwanyanga stock in mouse tissue and the carrier-status of the Senegal stock in mice.

The behaviour of two different stocks of Cowdria ruminantium was investigated in mice. The mouse-pathogenic Kwanyanga stock of C ruminantium was microscopically demonstrated in mice in capillary endothelial cells of the lung, spleen, kidney, liver and brain. Mice of the ninth passage of the Senegal stock, which is infective but not pathogenic to mice, were kept alive for a year. Their blood and homogenised spleens, inoculated intravenously, caused fatal heartwater in a goat. However, the Senegal stock could not be demonstrated microscopically in mice. These results indicate the possible role of rodents in the epidemiology of heartwater.

Animals↗

PubMed1989

[Borrelia burgdorferi from Ixodes ricinus ticks on Ameland].

Ixodes ricinus ticks collected from the North Sea Island of Ameland, the Netherlands, were screened for the presence of Borrelia spirochaetes. The present authors used IFAT on tick gut preparations and identified Borrelia in 31 per cent of the adult ticks and 16 per cent of the nymphs collected from the dunes and 45 per cent of the nymphs collected from the forests. In vitro cultivation of Borrelia sp. isolated from the adult ticks and its subsequent recognition by B. burgdorferi-specific monoclonal antibodies in western blots, verified that this pathogen is identical with B. burgdorferi, the causative agent of Lyme Disease. Further research is required to gain an insight into the epidemiology of the disease and to assess its medical and veterinary significance in the Netherlands.

Animals↗

PubMed1989

Monitoring of naturally acquired and artificially induced immunity to Amblyomma variegatum and Rhipicephalus appendiculatus ticks under field and laboratory conditions.

The ability of rabbits, goats and cattle to acquire immunity to the ixodid ticks Amblyomma variegatum and Rhipicephalus appendiculatus was studied under laboratory and field conditions. Rabbits were successfully immunized with crude salivary gland extract (SGE) and midgut extract (ME) obtained from flat or partly fed female R. appendiculatus ticks. The lowest numbers of larvae were produced by females fed on rabbits immunized with unfed midgut extract. Similar reductions in larval production could be induced after three infestations of rabbits with adult R. appendiculatus. Also, successive feedings of nymphs of R. appendiculatus on rabbits resulted in significantly reduced engorgement weights. Skin testing with SGE induced delayed-type hypersensitivity reactions, which could be correlated with immunity to R. appendiculatus in rabbits. Moreover, circulating antibodies were detected in rabbits with an ELISA using SGE of R. appendiculatus. Immunity to A. variegatum nymphs could be induced in rabbits by repeated infestations, but this failed in goats. Immunization of goats with midgut extract from adult A. variegatum did not protect against subsequent nymphal challenge, but strong skin reactions were noticed when adults ticks fed on immunized goats. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of SGE and ME from A. variegatum revealed the presence of 48 protein bands in SGE and 29 bands in midgut extract. Western blotting employing serum from a rabbit immune to R. appendiculatus recognized a number of bands in SGE from R. appendiculatus, but also in SGE of A. variegatum. Immunity acquired by cattle to ixodid tick infestations under field conditions was monitored by skin testing with SGE and western blot analysis. In general, cattle with the lowest tick numbers manifested the strongest delayed-type hypersensitivity responses. Finally, western blot analysis employing sera from tick-infested and tick-naive cattle could not be related to actual immune status.

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PubMed1989

Serotypes in Cowdria ruminantium and their relationship with Ehrlichia phagocytophila determined by immunofluorescence.

Two tick-borne rickettsial pathogens of ruminants, Cowdria ruminantium (causative agent of heartwater disease) and Ehrlichia phagocytophila (causative agent of tick-borne fever), were successfully cultivated in caprine or ovine neutrophilic granulocytes. Infected cultures were subsequently used as antigens in the indirect fluorescent antibody test. Low-level bilateral serological cross-reactions could be detected between Cowdria and Ehrlichia. In addition, comparison of five Cowdria stocks using immunofluorescence demonstrated the existence of distinct serotypes within the genus of Cowdria. It is concluded that the occurrence of these serotypes will considerably complicate the current serodiagnosis of heartwater.

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PubMed1989

Identification of an immunodominant antigenically conserved 32-kilodalton protein from Cowdria ruminantium.

Western blotting (immunoblotting) of Cowdria ruminantium antigens with goat or mouse antiserum identified a periodate-resistant, proteinase K-sensitive immunodominant antigen of 32,000 daltons. This protein, designated Cr32, could be demonstrated in goat choroid plexus infected with one of two different Cowdria stocks. Antisera against nine different Cowdria stocks from Africa and the Caribbean region recognized Cr32, which indicates that this protein contains conserved antigenic determinants.

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PubMed1988

Epidemiology of bovine babesiosis and anaplasmosis in Zambia.

The serological prevalence of bovine babesiosis and anaplasmosis in the traditional farming sector of six provinces of Zambia was determined using the indirect fluorescent antibody test (IFAT) for babesiosis and the card agglutination test (CAT) for anaplasmosis. Antibodies to Babesia bigemina occurred throughout the country whereas the prevalence of B. bovis followed the distribution of its tick vector Boophilus microplus which is limited to the north-eastern part of the country. Low numbers of B. bovis serologically positive cattle were demonstrated in central and southern Province. Anaplasma spp. occurred throughout Zambia but the overall percentages of positive sera were low ranging between 14.7% and 38.6% using the CAT. Two hundred sera were retested for anaplasmosis using an enzyme-linked immunosorbent assay (ELISA). Sero-prevalence rates were 1.5 to 2.3-fold greater with the ELISA than with the card agglutination test.

Agglutination Tests↗

PubMed1988

Quantitative correlation of parasitological and serological techniques for the diagnosis of Trypanosoma congolense infection in cattle.

A comparison was made between serological and parasitological techniques for the diagnosis of bovine trypanosomiasis in Zambia. Overall sero-prevalence rates as determined by IFAT and ELISA were respectively 2.7-fold and 2.9-fold greater then the percentage of samples found positive with the dark ground/phase contrast buffy coat technique (DG). The results obtained by the two serological techniques were found to be closely correlated (94.2%) agreement) and titres obtained by ELISA tended to be slightly higher than those obtained by IFAT. Linear regression analysis of the results obtained by the IFAT and DG techniques revealed a highly significant correlation. This finding would permit the use of only one of the techniques in an epidemiological survey and to extrapolate the results from the regression line.

Animals↗

PubMed1988

Morphogenetic diapause in Amblyomma variegatum (Acari: Ixodidae).

In southern Africa, Amblyomma variegatum Fabricius is characterized by a strict seasonal activity. Experiments were carried out to determine whether a diapause mechanism regulates this seasonality. Engorged A.variegatum females were exposed to controlled laboratory conditions or natural field conditions at different times of the year. Females exposed in a natural environment in September-October (short day) had significantly longer pre-oviposition periods than females exposed from November to March. The season in which the previous instar fed had no apparent effect on the engorgement or pre-oviposition periods of the females. Furthermore, artificial changes in photoperiod during and after female engorgement had no significant effects on pre-oviposition periods. It is tentatively concluded that the unfed female is the responsive stage to photoperiodic changes which induce diapause. Diapause could be terminated and oviposition induced by exposing females to a short period of chilling (18 degrees C for 48 h). It is concluded that a morphogenetic diapause mechanism exists in A.variegatum, which is probably induced by short day responses and terminated following rainfall and a concomitant decrease in soil temperature. The diapause, which occurs in females which fed early in the season, causes a delay in oviposition and therefore effectively synchronizes the life-cycle to ensure that eggs and larvae occur at a climatically favourable period.

Animals↗

PubMed1988

Antigenic differences between stocks of Cowdria ruminantium.

Stocks of Cowdria ruminantium from Senegal, Zambia and South Africa were compared in cross immunity tests in goats. The Senegal stock caused fatal heartwater in three of 10 goats immune to the South African reference stock Ball 3, and five others showed significant febrile reactions and recovered spontaneously. Four goats immune to the Senegal stock did not show any reaction on challenge with Ball 3. The stock from Zambia was fully cross-protective with Ball 3 in experiments with three goats, but these three goats, immune to the Zambia stock and to Ball 3, showed severe febrile responses upon further challenge with the Senegal stock. The Senegal stock was highly virulent for Dutch goats and there were exceptionally large numbers of rickettsiae in brain capillaries after death. This stock has been passaged eight times in mice, without causing disease; the presence of the organism in the mice was shown by subinoculating goats. The Senegalese stock of C ruminantium is the first stock outside South Africa against which the reference Ball 3 stock does not fully immunise.

Animals↗

PubMed1987

Ticks (Acari:Ixodidae) of the Blue and White Nile ecosystems in the Sudan with particular reference to the Rhipicephalus sanguineus group.

Twenty-four adult ixodid tick species, infesting livestock and some wildlife hosts along the Blue and White Nile in the Sudan, were identified. Three species, Boophilus geigyi, Rhipicephalus camicasi and R. bergeoni, were recorded for the first time from the Sudan. Tick numbers on indigenous breeds of cattle (Bos indicus) were relatively low, ranging between 17.1 and 40.5 per animal. Young cattle grazing with the herd carried significantly fewer ticks than older animals. With the exception of B. annulatus and R. simus, which have extended their distribution further north into Blue Nile, Gezira and Khartoum Provinces, the distribution patterns of the most important cattle ticks have been relatively unchanged over the past 30 years. The Rhicicephalus sanguineus group was represented by six species. R. camicasi was the only species present on cattle, sheep and goats in the north in Kassala and Khartoum Provinces, whereas this species occurred sympatrically with R. guilhoni and R. turanicus further south in Gezira and Blue Nile Provinces. In the Southern Region of the Sudan only R. turanicus and R. guilhoni were present, the latter being by far the predominant species, with peak activity towards the end of the rains in the Jonglei Canal Area. R. bergeoni was collected once, from cattle near the Ethiopian border in Blue Nile Province, whereas R. sanguineus sensu stricto was collected throughout the study area, from domestic dogs only. Finally, R. sulcatus was found once on a hare. The distributions of the common tick species are correlated with the occurrence of tick-borne diseases of domestic animals and recommendations for the control of tick-borne diseases and their vectors in the Sudan are given.

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PubMed1986

Biology of Rhipicephalus appendiculatus and R. zambeziensis and production of a fertile hybrid under laboratory conditions.

In some areas of Eastern and Southern provinces of Zambia Rhipicephalus appendiculatus and R. zambeziensis are sympatric, and numerous intermediate forms as well as typical R. appendiculatus and R. zambeziensis are found. Experiments were carried out in order to clarify the taxonomic status of the intermediate forms. Biology and hybridization capacities of two strains of R. appendiculatus (A and D) and one strain of R. zambeziensis (H) were studied. Infestations on rabbits and calves were performed at the beginning and at the end of the Zambian rainy season. The adults of both species showed preference for the bovine host and performed better at the end of the rainy season. A recently isolated strain of R. appendiculatus had notably higher larval production per unit engorgement weight than the strain that had been maintained for prolonged periods under laboratory conditions. R. zambeziensis produces fewer larvae and had longer development periods than R. appendiculatus. The two species cross-breed under laboratory conditions. A fertile hybrid is produced by R. zambeziensis females and R. appendiculatus males, whereas a sterile hybrid is a result of a reciprocal cross. Morphology of adults of the fertile hybrid (H/A) is indistinguishable from the maternal species, whereas adults of the sterile hybrid (A/H) are of maternal, paternal and intermediate forms. Larval production indices (LPI) vary from 0.4 to 3.7 for the H (females) X A (males) cross, approximately three-fold less than in the maternal species. For the reciprocal cross, LPI ranges from 0.1 to 2.7, five- to thirty-fold less than in the maternal species. The fertile hybrid has a higher LPI than both first crosses, and under the most favourable climatic conditions LPI is even higher than for the maternal species. Adults of the sterile hybrid rarely formed pairs. Only partially engorged female ticks detached, which produced no viable eggs. Both hybrids may occur in areas where the two species are sympatric. However, detailed field studies will have to be performed in order to gain knowledge on population dynamics, interbreeding and the vector role of the two species and their hybrids under field conditions.

Animals↗

PubMed1986

Transmission of a Trypanosoma sp. to cattle by the tick Hyalomma anatolicum anatolicum.

Hyalomma anatolicum anatolicum engorged nymphs and flat adults were collected from two areas in northern Sudan. Various developing stages of Trypanosoma theileri-like flagellates were observed in the engorged nymphs, freshly moulted adults and mature adults partially engorged on rabbits. When these ticks were applied to two calves, one calf became infected with the trypanosome. The parasites were observed for one day in the enlarged lymph node nearest to the tick-feeding site 5 days after the tick application. Subsequently the trypanosomes were re-isolated in vitro from the infected calf. Inoculation of a ground-up tick supernatant suspension from the infected batch of ticks containing 10(4) trypanosomes into a calf did not produce a patent infection.

Animals↗

PubMed1986

Bovine babesiosis (Babesia bovis infection) in Zambia.

Two cases of Babesia bovis, a parasite associated with the tick Boophilus microplus, are reported for the first time from the central part of Zambia. It is concluded that infected B. microplus ticks are occasionally introduced into central Zambia by tick-infested cattle from the north-eastern part of the country where B. bovis is endemic. The spread of B. microplus in Southern Africa in a westward direction is discussed and related to the epidemiology of bovine babesiosis in Zambia.

Animals↗

PubMed1986

Theileria taurotragi in Zambia.

Theileria sp. (Bwengwa) of low virulence was isolated by feeding R. appendiculatus ticks collected from the field on a susceptible calf and subsequently transmitted between cattle by R. appendiculatus ticks- Theileria sp. (Bwengwa) was shown to be T. taurotragi on parasitological, clinical and serological grounds. T. taurotragi is the fourth Theileria sp. shown to be present in Zambia.

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