Search

The ITRC is the official reference laboratory of both the International Commission on Trichinellosis (since 1988) and the International Office of Epizootics (since 1992). The ITRC was created as a repository for Trichinella strains and as a source of materials and information for international research in 1988. To date, about 900 isolates of human and animal origin from throughout the world have been examined and identified by new procedures developed at the ITRC or in collaboration with other institutions. Using material from this collection, the ITRC has provided a complete revision of the systematics of the genus Trichinella. The ITRC database can be consulted by accessing the web-site: www.simi.iss.it/trichinella/index.htm.

There are no published reports of domestic or sylvatic trichinellosis in Texas. The aim of the present survey was to determine the presence of Trichinella species in selected representative species of potential wildlife reservoirs in southern Texas. In 1998-99, tongues of 211 wild mammals were collected in southern Texas: 154 coyotes (Canis latrans), three bobcats (Lynx rufus), 32 racoons (Procyon lotor), 1 3 opossum (Didelphis marsupialis), four ocelots (Leopardus pardalis) and five wild boars (Sus scrofa). Presence of Trichinella sp. larvae was investigated by artificial digestion and larvae of positive samples were identified at the species level by a multiple-polymerase chain reaction analysis. Nine (5.8 %) coyotes had trichinellosis ; in the muscles of seven of these coyotes, the larvae were identified as Trichinella murrelli. This is the first report of sylvatic trichinellosis in Texas.

Domestic and sylvatic trichinellosis have frequently been documented in European regions of Russia, with the highest prevalence reported in wolves (Canis lupus). From 1998 to 2000, 75 carcasses of wolves shot by hunters were tested for Trichinella larvae, and 73 (97.3 %) of them were found to be positive. This very high prevalence of infection, the highest ever detected in a natural population of carnivores, could be explained by the human impact on the natural ecosystem. In fact, the diet of wolves living in the region under study mainly consists of carcasses of dogs and wolves, which are left in the forest or used as bait by hunters.

Non-detection of trees is an important issue when using single-scan TLS in forest inventories. A hybrid inference approach is adopted. Quoting from distance sampling, a detection function is assumed, so that the inclusion probability of each tree included within each plot can be determined. A simulation study is performed to compare the TLS-based estimators corrected and uncorrected for non-detection with the Horvitz-Thompson estimator based on conventional plot sampling, in which all the trees within plots are recorded. Results show that single-scan TLS provides more efficient estimators with respect to those provided by the conventional plot sampling in the case of low-density forests when no distance sampling correction is performed. In low-density forests, uncorrected estimators lead to a small bias (1%-6%), increasing with plot size. Therefore, care must be taken in enlarging the plot radius too much. The bias increases in forests with clustered spatial structures and in dense forests, where the bias levels (30%-50%) deteriorate the performance of uncorrected estimators. Even if the bias- corrected estimators prove to be effective in reducing the bias (below 15%), these reductions are not sufficient to outperform conventional plot sampling. Therefore, there is no convenience in using TLS-based estimation in high-density forests.Key words: plot sampling, TLS-based detection, distance sampling, hybrid inference, simulation study.La non-detection des arbres est un probleme important lors de l'utilisation d'un scanner laser terrestre (SLT) a balayage unique pour les inventaires forestiers. Une approche d'inference hybride est adoptee. En se fondant sur l'echantillonnage a distance, on peut deduire une fonction de detection permettant de determiner la probabilite d'inclusion de chaque arbre present dans chaque placette. Une etude par simulation est realisee pour comparer les estimateurs fondes sur le SLT qui ont ete corriges ou non pour la non-detection a l'aide de l'estimateur de Horvitz-Thompson, lequel est base sur un echantillonnage conventionnel de placettes dans lequel tous les arbres des placettes sont enregistres. Les resultats montrent que le SLT a balayage unique produit des estimateurs plus efficaces que ceux provenant d'un echantillonnage conventionnel de placettes dans le cas des forets a faible densite lorsqu'aucune correction d'echantillonnage a distance n'est effectuee. Dans les forets a faible densite, les estimateurs non corriges entrainent un leger biais (de 1 a 6 %), qui augmente avec la taille de la placette. Par consequent, il faut prendre garde de ne pas trop agrandir le rayon de la placette. Le biais augmente dans les forets ayant une structure spatiale regroupee et dans les forets denses, pour lesquelles la taille du biais (de 30 a 50 %) deteriore la performance des estimateurs non corriges. Meme si la correction du biais des estimateurs s'avere efficace pour reduire le biais (inferieur a 15 %), ces reductions ne sont pas suffisantes pour surpasser l'echantillonnage conventionnel de placettes. Par consequent, il n'y a pas d'avantage a utiliser une estimation fondee sur le SLT dans les forets a forte densite. [Traduit par la Redaction]Mots-cles : echantillonnage de placettes, detection par scanner laser terrestre (SLT), echantillonnage a distance, inference hybride, etude par simulation., 1. IntroductionTerrestrial laser scanning (TLS) has been demonstrated to be a promising tool for plot-level field inventories (e.g., Liang et al. 2011; Moskal and Zheng 2012; Kankare et al. 2015; [...]