A. Mannelli

Borrelia lusitaniae and Spotted Fever Group Rickettsiae in Ixodes ricinus (Acari: Ixodidae) in Tuscany, Central Italy

Abstract Prevalence of infection by Borrelia burgdorferi s.l. and spotted fever group (SFG) rickettsiae was estimated in host-seeking ticks in an area in Tuscany, central Italy, where Lyme borreliosis was reported in a forestry worker. B. burgdorferi s.l. was identified by polymerase chain reaction in 16.7% (95% CI = 10.3, 24.8) of Ixodes ricinus (L.) nymphs and 39.6% (95% CI = 26.5, 54.0) of adults. Borrelia lusitaniae accounted for 82.9% of positive samples, followed by Borrelia garinii (9.8%), Borrelia afzelii (2.4%), and Borrelia burgdorferi s.s. (2.4%). One Rhipicephalus spp. adult was infected with B. garinii (prevalence = 8.3%; 95% CI = 0.21, 38.5). Prevalence of infection by SFG rickettsiae was 38.5% (95% CI = 26.7, 51.4) in I. ricinus nymphs, 34.6% (95% CI = 22.0, 49.1) in I. ricinus adults, and 50% (95% CI = 21.1, 78.9) in Rhipicephalus spp. adults. Phylogenetic analysis showed the similarity of B. lusitaniae strains that were identified in this study and of a strain that was previously isolated from a human patient in Portugal. Results of this study confirm the dominance of B. lusitaniae in areas in the Mediterranean basin and the infection by SFG rickettsiae in I. ricinus.

Borrelia burgdorferi sensu lato Infection in Larval Ixodes ricinus (Acari: Ixodidae) Feeding on Blackbirds in Northwestern Italy

Abstract Birds belonging to 59 species (n = 1,206) were live captured in Piemonte, northwestern Italy, in 2001. Ixodes ricinus (L.) larvae were collected from 59 birds belonging to nine species, and nymphs were recovered on 79 birds belonging to 10 species. Eurasian blackbirds, Turdus merula L., had significantly higher levels of infestation by ticks than other passerine species. Larval I. ricinus of blackbirds peaked in summer, when prevalence was 39% (95% confidence interval 24.2–55.5) and mean number of ticks per host was 3.3 (1.6–7.2), whereas nymphs peaked in spring, when prevalence was 72.2% (54.8–85.8) and mean number of ticks per host was 6.9 (4.4–10.7). Immature I. ricinus were coincidentally aggregated on blackbirds, with 15 blackbirds feeding 67.4% of nymphs and 40.3% of larvae, and coinfestation by both stages was relatively high in summer: Kappa = 0.64 (0.40–0.88). Borrelia burgdorferi sensu lato was identified by polymerase chain reaction (PCR) in 58.3% (35.9–78.5) of larvae with engorgement ratio ≥3 that were collected from blackbirds. Larvae that were collected from other passerine species gave negative PCR results. Sixteen of 21 PCR-positive samples belonged to B. garinii (76.2%), and five (23.8%) were Borrelia valaisiana. Results of this study suggest that blackbirds play an important role as hosts for immature I. ricinus and as reservoir of Borrelia garinii in northwestern Italy.

Associations between dogs that were serologically positive for Rickettsia conorii relative to the residences of two human cases of Mediterranean spotted fever in Piemonte (Italy)

A geographic information system and K-function analysis were used to evaluate the spatial association of canine serological results for Rickettsia conorii, the causative agent of Mediterranean spotted fever (MSF), and clinical cases of MSF in humans in Piemonte, northwest Italy. The residences of dog owners were clustered in two rural villages in the province of Cuneo, where two human cases of MSF occurred in 1997 and 1998. Eighteen out of 116 dogs examined were positive by indirect immunofluorescent assay (IFA+, titre > or =1:160) for MSF. K-functions were compared for IFA+ dogs and for all dogs sampled. Monte Carlo and bootstrap simulations demonstrated that clustering of IFA+ dogs was significantly greater than clustering of all dogs, at distances of less than 0.6 km from human cases of MSF. Logistic regression analysis indicated that the risk of being IFA+ was highest for dogs residing within the first quartile of distance (0.7 km) from human cases of the disease, and for dogs that were not confined. However, year and season of blood collection were not associated with IFA status. It was concluded that a relatively high dog population density along with a rural or semi-rural environment favours the occurrence of emergent foci of MSF in the province of Cuneo.

Acarological risk of exposure to agents of tick-borne zoonoses in the first recognized Italian focus of Lyme borreliosis.

Acarological risk was calculated as the probability of encountering at least one host-seeking Ixodes ricinus tick infected by the pathogen Borrelia burgdorferi sensu lato, in 100 m transects in the province of Genoa, Italy. The seasonal pattern of I. ricinus was studied using generalized estimating equations (GEE) with negative binomial error, to consider overdispersion of tick counts and repeated sampling of the same dragging sites from April 1998 to March 1999. Prevalence of infection by B. burgdorferi s.l. was evaluated by PCR and hybridization with genospecies-specific probes. Acarological risk (R) peaked in April (R = 0.2, 95% CI 0.13-0.26) and November (R = 0.29, 95% CI 0.10-0.46). Borrelia garinii and B. valaisiana were the most common genospecies at our study site suggesting a major role of birds as reservoirs. DNA from Anaplasma phagocytophilum, the agent of granulocytic ehrlichiosis in humans and animals, was amplified from an adult I. ricinus.

Evaluation of the risk of neighbourhood infection of H7N1 Highly Pathogenic Avian Influenza in Italy using Q statistic

Exposure to the risk of neighbourhood infection was estimated for the H7N1 Highly Pathogenic Avian Influenza (HPAI) epidemic that affected Northern Italy between 1999 and 2000. The two most affected regions (Lombardy and Veneto) were analyzed and the epidemic was divided into three phases. Q statistics were used to evaluate exposure to the risk of neighbourhood infection using two measures. First, a local Q statistic (Qikt) assessed daily exposure for each farm as a function of the number of neighbouring infected farms that were in their infectious period, weighted by the distance between farms. This allowed us to identify the daily time course of risk for each farm and, at any given time, local groups of farms defined by high risk. Second, for each farm a summary statistic of exposure risk within each phase (Qiph) was obtained by summing Qikt over the duration of each phase. This allowed identification of farms defined by persistent, high exposure risk within each phase of the epidemic. Statistical significance was evaluated using conditional Monte Carlo simulation, and significant values of Qiph were mapped to assess the variation of the risk of neighbourhood infection through the phases. Qikt was larger for farms in Lombardy and the reduction of exposed farms was more marked for Veneto. Although the highest value of Qiph was observed in Veneto, in each phase most of the significant values were in Lombardy. In the last phase of the epidemic, a large reduction in the number of farms significantly exposed to the risk of neighbourhood infection was observed in the Veneto region, along with generally low values of Qiph. This may be explained by differences in control measures in the two regions, including pre-emptive slaughtering of farms considered at high risk of infection. The Q statistic allowed us to quantify geographic, time-dynamic variations in exposure to neighbourhood infection, and to generate hypotheses on the efficacy of control measures.