Spiroplasmas and spongiform encephalopathies.
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Biomedical subjects
Publications and source records attributed to C Chastel.
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Four consecutive epidemics of keratoconjunctivitis caused by adenovirus 8 (Ad8) occurred over a 5-year period in Brest, France. A selection of 30 strains isolated during this period was studied by DNA restriction enzyme analysis using nine restriction enzymes. BglI and SacI were the most discriminative enzymes and allowed the recognition of four DNA variants, all different from the prototype strain Trim. Within each of the epidemics, the strains tested could not be distinguished in this analysis. Between strains from different epidemics differences in DNA structure could be detected however. Thus, the Ad8 epidemics of 1983/1984, 1984, 1987, and 1988 appear to have been due to DNA variants Ad8/D7, D8, D9, and D10, respectively. These results demonstrate that the DNA of Ad8 seems to display a considerable variability, comparable to that observed with Ad7 and Ad21. As has been described for Ad7, Ad21 and Ad41, successive DNA variants of Ad8 prevail during one or more years, and are then replaced by other, newly emerging variants sometimes associated with epidemics.
From 1981 to 1990, 96 confirmed hospital cases of imported malaria occurred in Brest. An important increasing of the annual number was observed in 1986. A high proportion of infection was due to Plasmodium falciparum, mainly from black Africa. Most of the patients was French young men, without or with inadequate chemoprophylaxis. Every case of malaria due to P. falciparum appeared during the 2 months following their return from an endemic area. Two patients had a clinical profile of visceral evolutive malaria and 5 a cerebral malaria. Three patients died.
Using alternate passages of cultivation in vitro at 37 degrees C and in suckling mice following intracerebral inoculation, a tabanid spiroplasma was demonstrated capable of multiplication and persistence in mice for 6 successive passages, without production of specific antibody. This is the first report of a spiroplasma from a common flying haematophagous arthropod shown to produce persistent infection of a mammal.
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Strain A56 of the bee pathogen Spiroplasma melliferum was isolated from a honeybee (Apis mellifera) during ecological studies on mosquito spiroplasmas in Savoie (France). When inoculated intracerebrally (i.c.) into 48-h old suckling mice, this strain was found to replicate to very high titres and to persist in brain for up to 9 months in one individual. We attempted to increase the "neurotropism" of A56 by sequential i.c. passages. During the first two passages, multiplication of the organisms was observed at very high titres in suckling mouse brain (10(7) to 10(11) CCU/ml) generally without the appearance of antibody, thus mimicking the so-called "immunological tolerance" phenomenon. Intracerebral multiplication of A56 decreased during the third passage (10(2) to 10(4) CCU/ml) and ceased during the fourth passage. Spiroplasma multiplication in brain was apparently well tolerated, since brain lesions were minimal and clinical symptoms were limited to a clear, but only rarely significant, delay in growth curves of inoculated versus non-inoculated mice. Progressive spongiform encephalopathy was never observed. Strain A56 S. melliferum appears as the second spiroplasma, after the tick-derived Spiroplasma mirum capable of multiplying in both invertebrate and vertebrate hosts.
Intrathoracic inoculation with the mosquito spiroplasma, Spiroplasma taïwanense Abalain-Colloc et al., was found to reduce significantly the survival of adult male and female Aedes aegypti (L.) and Anopheles stephensi Liston. This spiroplasma also reduced significantly the flight capacity of adult female Ae. aegypti 5-8 d after inoculation and adult female An. stephensi 4 d after inoculation. Adult female An. stephensi were incapable of flight 5 d after inoculation. As such, S. taïwanense joins Bacillus thuringiensis and B. sphaericus as bacteria known to be pathogenic for mosquito vectors.
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Helical replicative forms, but not the persistent non-replicative forms, of Spiroplasma taiwanense Abalain-Colloc et al. (isolated from the mosquito Anopheles sinensis Wiedemann in Taiwan) were shown to reduce significantly the survival of Aedes aegypti (L.) mosquito larvae reared in 10 ml of water with 0.3 ml of S.taiwanense suspensions added on days 0 and 3. The suspensions contained, respectively, helical forms at a concentration of 10(9) Colour Change Units (CCU)/ml and persistent forms at 10(6) CCU/ml. It is suggested that S.taiwanense, or toxins produced from it, are potentially useful for use in integrated mosquito control programmes.
Eighteen patients with typical Herpes simplex virus dendritic keratitis confirmed by viral isolation were treated with corneal collagen shields presoaked with trifluorothymidine for 15 minutes and trifluorothymidine eye drops 5 times daily. The average healing time was 2.9 days (range 1-7 days). No allergic reactions were observed. Toxic punctate keratitis occurred in 3 eyes. The results of this open study suggest that the effect of collagen corneal shields in conjunction with trifluorothymidine shortens the average epithelial healing time compared with other studies that have used antiviral drugs alone.
An increasing number of experimental findings suggest that Spiroplasma taiwanense (Class Mollicutes) has considerable potential for inclusion in integrated mosquito vector control programmes. These experimental findings are outlined in conjunction with preferred strategies for its eventual use as a biological control agent.
The optimal management of herpes simplex stromal keratitis and uveitis is controversial. Thirty-two patients with presumptive herpetic anterior uveitis without active corneal inflammation received 3% acyclovir ophthalmic ointment five times daily and acyclovir 200mg orally five times a day. Eight of 18 patients (44.4%) who had received corticosteroids deteriorated over the first five days of therapy; one of 14 patients (7.1%) without previous corticosteroid use worsened during this time (P less than .05). The mean healing time was similar in these two groups. These results suggest that antiviral therapy may be first-line treatment in patients with herpetic keratouveitis who have not received corticosteroids.
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Sera from 269 wild rabbit (Oryctolagus cuniculus L.) trapped in 1985 and 1986 in Camargue and Vaucluse, France, were studied for antibody against 9 arboviruses. By inhibition haemagglutination test, positive reactions were found only against West-Nile (0.37%). By complement fixation test, antibodies were detected against Eyach (0.92%) and Tribec (0.46%). These results are discussed according to arboviruses isolated in France, to previous serosurveys in rabbits and other mammals and to potential vectors known to occur in France. Potential impact on rabbit population is also discussed.