Guidelines for the diagnosis of tick-borne bacterial diseases in Europe.

Ticks are obligate haematophagous acarines that parasitise every class of vertebrate (including man) and have a worldwide distribution. An increasing awareness of tick-borne diseases among clinicians and scientific researchers has led to the recent description of a number of emerging tick-borne bacterial diseases. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 11 tick-borne human bacterial pathogens have been described in Europe. Aetiological diagnosis of tick-transmitted diseases is often difficult and relies on specialised laboratories using very specific tools. Interpretation of laboratory data is very important in order to establish the diagnosis. These guidelines aim to help clinicians and microbiologists in diagnosing infection transmitted by tick bites and to provide the scientific and medical community with a better understanding of these infectious diseases.

[New distribution of tick-borne diseases in temperate countries]. / Redistribution des maladies transmises par les tiques en zone tempérée.

Since 20 or 30 years, emerging tick-borne diseases are regularly reported. Recent data show that at the same time, we have to expect a change in distribution of some disease as the European tick-borne encephalitis, due to the strong relation between ticks cycle and temperatures for the transmission of this virus.

[Emergence of tick-borne diseases in temperate countries]. / Emergence des maladies transmises par les tiques en zone tempérée.

Since a long time, many human tick-borne pathogens are known, but since 20 or 30 years, emerging tick-borne diseases are regularly reported. In temperate countries, all emerging diseases are Bacteriosis : six Rickettsiosis, one Ehrlichiosis, one Anaplasmosis and one Borrelia Spirochetosis.

Methodology for sampling questing nymphs of Ixodes ricinus (Acari: Ixodidae), the principal vector of Lyme disease in Europe.

To assess the Lyme borreliosis vector population density we set up a methodology for sampling the Ixodes ricinus L. population host questing on the vegetation. We focused on the collection of the nymphal stage, which is the principal stage of disease transmission to humans. This study was carried out in Rambouillet forest (Yvelines, France) where seven study areas were demarcated. These areas are maximally homogeneous for plant species using a finer scale than the phytosociological classification as defined by the method of landscape diagnostics. Out of 23 collections performed from March 1997 to May 1998, 2,906 I. ricinus nymphs were collected. The sampling technique chosen was the cloth lure technique. The technical parameters were studied and fixed (cloth type, cloth size, sample size, researcher position). It appeared that toweling was the best cloth type to optimize the number of ticks collected; the position of the researcher had no effect on tick samples. To satisfy the criteria for correct sampling, we studied representativity, randomness, and nonselectivity of our methodology. The spatial distribution of nymphs in a homogeneous area was close to random and thus very few subsamples were needed to obtain a relative density which was representative. No significant differences were found between random samples and following transect samples; and nonselectivity was totally satisfied because we only worked on questing nymphs. We grouped the samples that presented no significant differences to attribute a density index, which varied from 0 to 5. This methodology, applied with the same parameters, offers potential for producing comparable results from studies in different geographical areas and at different times of the years.

Detection of spirochaetes of Borrelia burgdorferi complexe in the skin of cervids by PCR and culture.

To determine whether deer may play a role in the cycle of the Lyme disease spirochete Borrelia burgdorferi, we sought evidence for the presence of the pathogen in skin of deer and roe deer. Biopsies of 2 mm3 were taken at four different levels from nail to tarsus. A total of 50 animals (200 biopsies) were shot in the Lyme disease foci of Rambouillet during the hunting season 1995-1996 and 1996-1997, from the beginning of November to the end of February. Borrelia burgdorferi s.l. DNA was detected by PCR in 18 biopsies from 14 animals (28%). Borrelia burgdorferi s.str. was predominant (50%), followed by B. garinii (30%) and B. afzelii (10%). Multiple infections were detected in four animals: same species at different levels or two different species from the same biopsy or from different biopsies from the same foot. A total of 125 biopsies were cultivated on BSKH medium. Cultures at 160 days revealed immobile spiralled forms in 10 cultures. One, from a deer killed at the end of December, was confirmed by PCR as B. burgdorferi s.str. These results, frequency of detection of spirochetes by PCR in the skin, multiple infections and alive spirochetes in biopsies taken out side the season of activity of ticks strongly suggest an affinity of Lyme disease spirochetes for skin of cervids.

Temporal distribution of the annual nymphal stock of Ixodes ricinus ticks.

The human risk of contracting Lyme disease or other tick borne diseases transmitted by the tick species Ixodes ricinus is broadly linked to the tick nymph density. The study was performed in Rambouillet forest (Yvelines, France), a known focus of Lyme borreliosis, from January 1997 to December 1999. We used a nymph sampling methodology which permitted us to obtain a monthly nymph density index (from 0 to 5). Studying the seasonal nymph and larval activity patterns and estimating the larval developmental duration, we demonstrate the existence of an annual nymphal stock. Secondly, we elucidate how this stock is distributed throughout the year, month by month. Its distribution is principally dependent on two factors: the monthly mean ambient temperature and the proportion of active nymphs which find a host each month. Expected monthly nymph densities derived from a theoretical model describing the temperature-dependent stock distribution gave a good fit to the observed densities, accounting for between 76-86% of the monthly variation in observed nymph densities. Predicting the temporal distribution of nymph activity within a stable Lyme borreliosis focus enables more precise identification of risk periods.

Density of deer in relation to the prevalence of Borrelia burgdorferi s.l. in Ixodes ricinus nymphs in Rambouillet forest, France.

The Rambouillet Forest, a Lyme disease-endemic area near Paris, France, was surveyed from September 1994 to October 1995 to determine the risk periods and zones for humans. Firstly, during the period of Ixodes ricinus activity, abundance of nymphs is greater in spring than in autumn. Secondly, we observed significant variation in nymphal abundance between zones according to the density of cervids. The polymerase chain reaction (PCR) was used to detect DNA of Borrelia burgdorferi sensu lato in 461 unfed nymphs. DNA was detected in 38 nymphs (8.2%). By genospecific PCR based on the OspA gene, we detected the three pathogenic spirochetes with occurrences of 10.3, 31.1 and 58.6 for B. burgdorferi s.s., Borrelia garinii and Borrelia afzelii, respectively, indicating that B. afzelii is probably the main Borrelia species in the Rambouillet Forest. Finally, 11.5% of positive nymphs exhibited a double infection. Infection rates of I. ricinus nymphs by B. burgdorferi s.l. were not significantly different throughout the year for a given area, indicating that the risk periods of acquiring Lyme disease are mainly linked to nymph activity and correspond to spring and autumn. Likewise infection rates of nymphs were not significantly different between zones with a high density of deer (more than 100 animals per 100 ha) and zones with lower deer density (less than 20 animals per 100 ha). In addition to the role of deer as an amplifier of tick populations, these data indicate that zones with a high density of cervids should be considered as higher risk areas.

[Human urinary myiasis caused by Fannia canicularis (Diptera, Muscidae) larvae in Algeria]. / Myiase urinaire humaine à larves de Fannia canicularis (Diptera, muscidae) en Algérie.

BACKGROUND: Human urinary myiasis is caused by fly larvae which complete their entire cycle in the human body. CASE REPORT: A 37-year-old woman living in a village near Sidi Bel Abbes (Algeria) developed a parasite syndrome caused by Fannia canicularis larvae. About twenty larvae specimens were collected during her hospitalization. Larvae were emitted for 2 weeks after a 6-day treatment with cefotaxime for urinary tract infection. DISCUSSION: Urogenital myiasis is almost always subsequent to conditions of poor personal hygiene. In this case authentic larvae infestation was evidenced. The diagnosis of true urinary myiasis was confirmed by repeated emissions of different larval stages including the nymph.

[Protective effect of clothing impregnated with permethrin against D. reticulatus and D. marginatus in an open biotope of central western France]. / Effect protecteur de vtements imprégnés de perméthrine vis-à-vis de D. reticulatus et D. marginatus dans un biotope ouvert du centre-ouest de la France.

During the period of major tick activity, in April and May 1998, in the Saint-Maixent l'Ecole area of Poitou, a comparative study was carried out in order to evaluate the protective effect of garments impregnated with permethrin cis/trans 25/75. Three groups of soldiers made up respectively of 208, 218 and 427 men were involved for 2 or 3 days in this experiment. Respectively 107, 107 and 215 wore impregnated uniforms. Out of a total of 319 ticks, 3 were lxodes ricinus, 305 Dermacentor marginatus and 11 D. reticulatus. There was a significant difference in both the intensity (number of ticks per individual, P < 0.0001) and prevalence (number of individuals with ticks, P < 0.001) of ticks on individuals between impregnated and non impregnated uniforms. The repellent effect of permethrin on ticks was observed at the site of preferential tick attachment (normally the head of the host for these two species of Dermacentor in France) where the number of ticks was significantly lower in impregnated uniforms.

[Lyme borreliosis, emergent disease linked with the environment]. / La borréliose de Lyme, maladie émergente liée à l'environnement.

After a short historical presentation of the discovery of the pathogen and its vector, the authors present the current data on bacterial and acarologic taxonomy. Then they describe their results to assess the mechanisms of circulation of the bacteria in the forests of Ile-de-France, particularly in the forest of Rambouillet. The combined study of abundance and infection frequency of the vectors, small mammals and cervids leads to the characterization of periods and areas of higher risk. The risk periods correlate with high density of I. ricinus nymphs. The risk areas correspond to those of high density of cervids. The role of reservoir of small mammals is confirmed, to the one of large mammals, so debated, is clearly demonstrated.

[First Algerian case of human otomyiasis from Chrysomya bezziana]. / Premier cas algérien d'otomyiase humaine à Chrysomya bezziana.

In Algeria, Human myiasis, essentially ophtalmomyiasis, are known for a long time. Most of cases are due to Oestrus ovis. In this papers the authors report, in a shepherd, the first case of otomyiasis due to Chrysomya bezziana larvae, a species still unknown in North Africa. This observation which indicates the presence of the species in a Northern part of Algeria is also the first report of the insect outside of its endemic traditional area.

Prevalence of antibodies to Borrelia burgdorferi in forestry workers of Ile de France, France.

A cross-sectional sero-epidemiological study was conducted on forestry workers, a high risk population for Lyme borreliosis. The prevalence of seropositive forestry workers (indirect immuno fluorescence assay) is 15.2% (n = 211). Almost 70% of participants reported a history of tick bite. Among districts, high seroprevalences were observed in Fontainebleau and Rambouillet; two sites of high risk for Lyme borreliosis. However, clinical prevalence of the disease is very low. During the investigation no active Lyme borreliosis was observed. Thus, asymptomatic infection predominates.

Use of enzyme-labelled protein G assay for the detection of anti Borrelia burgdorferi antibodies in wild animal sera.

A modified ELISA was developed for the detection of anti-Borrelia burgdorferi (Bb) IgG antibodies in wild animal sera based on an Enzyme-Labelled-protein G Assay (ELGA). Microplates were coated with an extract of Bb sensu stricto strain (SVI) as antigen. Specific antibodies of the serum samples were detected by a peroxidase-labelled-protein G. Using comparative immunodiagnosis by means of a passive hemagglutination test (HA), ELGA was tested on 82 roe-deer blood samples. A correlation was found between the two methods (r = 0.66). Good reproducibility of titers was observed by ELGA technique. A minimal cross-reactivity was discovered with Leptospira. ELGA could facilitate the recognition of specific antibodies in collections of wild animal sera.

Infection of Ixodes ricinus (Acari:Ixodidae) by Borrelia burgdorferi in Ile de France.

Free-living nymphs and adults from Rambouillet and Fontainebleau, 2 major forests of Ile de France, were collected to determine the infection rates of Ixodes ricinus L. by Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt & Brenner). Field-collected I. ricinus nymphs and adults were screened for the presence of B. burgdorferi using direct fluorescent antibody assay. The infection rates of nymph, male and female were 12.4% (314), 2.8% (35), and 2.9% (34). No difference in infection rates of nymphs among sites were detected. Spirochetes was isolated from both sites. Isolates from Rambouillet and Fontainebleau were identified as B. burgdorferi sensu stricto and B. garinii, respectively (Baranton, Postic, Saint-Girons, Boerlin, Piffaretti, Assous, and Grimont).

The Alsatian tick-borne encephalitis focus: presence of the virus among ticks and small mammals.

An extensive epidemiologic survey was carried out from 1970 to 1974 in order to understand the condition of circulation of tick-borne encephalitis virus between ticks and small mammals in the Alsatian focus, France. The virus has been isolated from Ixodes ricinus adult ticks (30 lots out of 369, representing a total of 5617 ticks), and from Ixodes ricinus nymphs (4 lots out of 251, representing a total of 8587 ticks). The virus has also been isolated from 11 pools of rodent organs (out of 3361 rodents), and HI antibodies were detected in 21 out of 8735 rodent specimens. The virus has never been detected in rodent blood, nor in 10,298 ticks collected engorged from 1505 vertebrate hosts. These results show that Alsatian tick-borne encephalitis focus is stable since the activity of the virus is detected every year, and that the focus is an extended one since the virus is isolated from 5 of 6 study sites, as well as in several control sites.

[Comparative study of dengue 2 virus replication and isoenzymes in two strains of Aedes aegypti]. / Etude comparée de la réplication du virus de la dengue 2 et des isoenzymes chez deux souches d'Aedes aegypti.

This study, dealing with two strains of Aedes aegypti from Vietnam and French Guiana, shows the variability of the genes coding for 11 isoenzymatic systems and the replication of the dengue 2 virus in parenterally infected mosquitoes. Slight differences are observed in the characteristics of viral replication. No clear correlation is shown with enzymatic patterns which appear widely different from one strain to the other with four of the enzymes studied.

[Lyme disease: epidemiology]. / Maladie de Lyme: épidémiologie.

Lyme disease, known primarily from North America, with three main foci in the United States, and from temperate Europe, particularly in France, seems to be increasing in incidence. Wherever it is known to exist, it has become the most prevalent tick-borne disease of man. The natural cycle of the etiologic agent, Borrelia burgdorferi, involves ticks as vectors and wild rodents as reservoirs. In infected areas, everyone walking or, especially, working in forested areas is at risk of tick bites, especially from May to October.