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Biomedical subjects

E Camus

Publications and source records attributed to E Camus.

At least 73 records · Page 4Linked to original sources
PubMed1988

[The detection of rare cellular events using scanning cytometry].

Preliminary studies are presented on the detection of the rare event cell using the Samba 200 cell image analyzer. The simple models used permitted us to define the technical parameters of this detection. It appeared possible to detect as low as one cell per 3.10(6).

Densitometry↗
PubMed1987

Heartwater serology: some problems with the interpretation of results.

Antibodies in the sera of domestic ruminants that have been infected with Ehrlichia bovis and other ehrlichial agents cross-react with the Kümm strain of Cowdria ruminantium used in the indirect fluorescent antibody test as antigen. These cross-reactions are also shown by the Elisa test in which the Ball 3 strain of the heartwater agent is used as antigen.

Animals↗
PubMed1987

Danger of introducing heartwater onto the American mainland: potential role of indigenous and exotic Amblyomma ticks.

The existence of heartwater on 3 islands of the Central Lesser Antilles and the presence of an efficient vector originating from Africa, Amblyomma variegatum, on most of the islands of this region constitute a serious threat for livestock on the American mainland. The disease can be introduced there either by infected animals or infected ticks. The most likely way is probably the transportation of domestic animals which are heavily infested by ticks. Due to the low rate of infection of ticks in endemic areas and the low rate of infestation of wild animals by ticks, the risk of transportation by migratory birds (among which the cattle egret is the most important) seems negligible compared with domestic animals, especially ruminants and dogs. The establishment and spread of the disease on the mainland could result from indigenous American Amblyomma species, of which at least 2, Amblyomma cajennense and, more especially, Amblyomma maculatum, are experimental vectors. The biological and ecological features of these ticks conform to some extent with the characteristics necessary for them to act as vectors. They are widespread and sufficiently well adapted to ruminants to ensure the continuation of the epidemiological cycle. Disease could evolve in wild life (deer) or, as seems more likely, in livestock, of which the population density is very high on most of the mainland. However, the establishment of the disease is more likely to occur if the well adapted vector of heartwater, Amblyomma variegatum, is introduced as well. This exotic species would find environmental conditions favourable for its survival and spread in most of the tropical and subtropical Western Hemisphere. Protection of the American mainland and the disease-free islands of the area must be based on strict control of domestic animal movement in the Caribbean, on the decrease of the vector population by tick control campaigns and, if possible, on the eradication of Amblyomma variegatum from the focus of heartwater on the islands.

Animals↗
PubMed1987

Diagnosis of heartwater in the live animal: experiences with goats in Guadeloupe.

A presumptive diagnosis of heartwater in the living animal can be based on clinical and epidemiologic observations. In Guadeloupe, heartwater can be confused with haemonchosis in goats or cerebral babesiosis in cattle. Confirmation of the clinical diagnosis by brain biopsy is useful in experimental infections but is hardly applicable in the field. Positive results were obtained from 92% of animals 16 to 18 days after experimental infection. In febrile animals the best results were obtained between the 3rd and 6th days of the thermal response. Diagnosis can also be supported by serological tests. These are useful for monitoring experimental infections and for checking recovered animals in the field. Nineteen goats out of 27 were negative on Day 1 of the febrile reaction but positive a week later. The remaining 8 goats were positive on Day 1 and had greatly increased antibody titres a week later. Confirmation of a diagnosis can also be achieved by subinoculating into susceptible animals either blood or suspensions of ticks collected from suspect animals and then homogenized. Ticks that have engorged on a suspect animal can be allowed to moult and then fed on a susceptible animal to test their infectivity. These methods are time consuming but useful for heartwater surveys.

Animals↗
PubMed1987

Genetic resistance of Guadeloupe native goats to heartwater.

The resistance rate of different populations of the same breed of creole Guadeloupean goats to Cowdria ruminantium infection varied greatly depending on the previous heartwater history of each population. After experimental infection of goats removed decades ago from endemic areas, the observed resistance rate was 25%, while it was 54% in a population that had been isolated from the disease for 10 years and reached 78% in a flock actually exposed to heartwater. This resistance seems to be under genetic control as sex and paternity were the most important factors which could explain resistance in a group of 90 kids of the same flock, tested under controlled conditions. Resistance rate varied greatly (20-83%) depending on the sire, with a heritability estimate of 0.49 for half sibs and 0.85 for full sibs. A recessive sex-linked gene could be involved in the genetic determination of this resistance. From these observations, it can be stated that in endemic heartwater areas, each population, i.e. each flock, will have developed resistance at a definite rate according to population, age and the extent of past and present exposure to the disease, through a natural selection of resistant lines. Populations removed from exposure to heartwater will progressively lose their ability to resist infection through an increase in the frequency of susceptible stock. If our hypothesis of a recessive sex-linked gene is proved correct, it should be easy to select for improved resistance to the Guadeloupe breed of goat to heartwater.

Animals↗
PubMed1987

Epidemiology of heartwater in Guadeloupe and in the Caribbean.

At present, heartwater in the Caribbean is known with certainty only on Guadeloupe, Marie Galante and Antigua; the first 2 islands are widely infected. The most important factors responsible for particular aspects of heartwater in Guadeloupe are: Cowdria ruminantium of high virulence. A very resistant cattle population (Creole), not normally clinically affected. A fairly susceptible goat population (Creole) (22% goats born in endemic areas die after experimental inoculation) which, fortunately, includes breeding lines with inherited resistance characteristics. Amblyomma variegatum which is present all over the island and all through the year, but with a low infection rate (1-2% of adult ticks are infected) because of the short period of rickettsemia in infected animals. The low rate of tick infection results in a low endemicity of the disease. For goats, the epidemiologic situation can be regarded as unstable because the low rate of infection in ticks does not allow a natural immunization of the majority of young kids when they still have a non-specific resistance. The possible evolution of heartwater in the Caribbean and in the United States in considered.

Animals↗
PubMed1987

The reservoir status of goats recovered from heartwater.

Experiments were conducted with Creole goats and Amblyomma variegatum ticks in Guadeloupe to investigate whether it is possible to transmit Cowdria ruminantium to susceptible hosts with nymphs fed in the larval stage on recovered goats. Of 88 batches of larvae fed after the return of the goats' temperature to normal, or after challenge or immunosuppression, only the 9 batches of larvae fed during the febrile reaction, 2 batches applied 2 and 3 days respectively after recovery, and a single batch applied 5 days after challenge, became infective. On average, blood appears to be infective for A. variegatum larvae for only an 8-day period associated with the temperature reaction following a primary infection. Recovered goats are not reservoirs of Cowdria, even if--with one exception in our experiment--they are reinfected after recovery.

Animals↗
PubMed1985

Heartwater in the Caribbean: isolation of Cowdria ruminantium from Antigua.

Adult Ambylomma variegatum ticks were collected from 184 cattle, 13 sheep and one goat in Antigua, and ground in phosphate buffered saline. The resultant supernates were cryopreserved in liquid nitrogen. Five supernate pools, each derived from approximately 100 ticks collected from different herds, were thawed and each was inoculated intravenously into a separate experimental goat. One goat exhibited a febrile response with Cowdria ruminantium demonstrable in brain biopsies; after recovery, this animal showed no reaction to a lethal challenge with a Guadeloupe isolate of C ruminantium.

Animals↗