Adriano Casulli

Rescue of a severely bottlenecked wolf (Canis lupus) population by a single immigrant.

The fragmentation of populations is an increasingly important problem in the conservation of endangered species. Under these conditions, rare migration events may have important effects for the rescue of small and inbred populations. However, the relevance of such migration events to genetically depauperate natural populations is not supported by empirical data. We show here that the genetic diversity of the severely bottlenecked and geographically isolated Scandinavian population of grey wolves (Canis lupus), founded by only two individuals, was recovered by the arrival of a single immigrant. Before the arrival of this immigrant, for several generations the population comprised only a single breeding pack, necessarily involving matings between close relatives and resulting in a subsequent decline in individual heterozygosity. With the arrival of just a single immigrant, there is evidence of increased heterozygosity, significant outbreeding (inbreeding avoidance), a rapid spread of new alleles and exponential population growth. Our results imply that even rare interpopulation migration can lead to the rescue and recovery of isolated and endangered natural populations.

Combined use of maternal, paternal and bi-parental genetic markers for the identification of wolf–dog hybrids

The identification of hybrids is often a subject of primary concern for the development of conservation and management strategies, but can be difficult when the hybridizing species are closely related and do not possess diagnostic genetic markers. However, the combined use of mitochondrial DNA (mtDNA), autosomal and Y chromosome genetic markers may allow the identification of hybrids and of the direction of hybridization. We used these three types of markers to genetically characterize one possible wolf–dog hybrid in the endangered Scandinavian wolf population. We first characterized the variability of mtDNA and Y chromosome markers in Scandinavian wolves as well as in neighboring wolf populations and in dogs. While the mtDNA data suggested that the target sample could correspond to a wolf, its Y chromosome type had not been observed before in Scandinavian wolves. We compared the genotype of the target sample at 18 autosomal microsatellite markers with those expected in pure specimens and in hybrids using assignment tests. The combined results led to the conclusion that the animal was a hybrid between a Scandinavian female wolf and a male dog. This finding confirms that inter-specific hybridization between wolves and dogs can occur in natural wolf populations. A possible correlation between hybridization and wolf population density and disturbance deserves further research.

Genetic variability of Echinococcus granulosus sensu stricto in Europe inferred by mitochondrial DNA sequences

The genetic diversity of Echinococcus granulosus sensu stricto (s.s.) metacestodes from four European countries was evaluated by the DNA sequence analysis of the cytochrome c oxidase subunit 1 (cox1) mitochondrial gene. Of the 312 organisms investigated, 132 were from Bulgaria, 35 from Hungary, 89 from Italy and 56 from Romania. Considerable intraspecific variation was observed in the mitochondrial cox1 sequences: 24 haplotypes were detected in the Eastern European population and seven in the Italian population. The Eastern European population parsimony network displayed a star-like features consisting of the most common haplotype EG1 (G1 genotype) and the three major haplotypes: EG2, EG3 and EG4. The EG1 was also the major haplotype in the Italian population network, though with a higher prevalence (73%) compared to the Eastern European network. The percentage of the population constituted by the G1 genotype was used as an indirect index to evaluate the genetic diversity within E. granulosus s.s. populations of Eurasia. A clinal correlation between the percentage of the G1 genotype and the geographical regions of Eurasia was observed: the G1 genotype is highly represented in the Mediterranean Basin; it decreases in Eastern Europe and South-West Asia and increases in China. This clinal correlation could reflect the spreading of livestock domestication from Southern-Western Asia during the Neolithic period, beginning around 12,000 BC.

Hunting Practices Increase the Prevalence of Trichinella Infection in Wolves From European Russia

From 1998 to 2000, 184 animals (82 wolves, 29 red foxes, 55 mustelids, 5 raccoon dogs, and 13 domestic dogs), mainly shot by hunters in the Tvier and Smoliensk regions of northwest European Russia, were tested for Trichinella larvae; 98 animals (53.3%) were found to be positive. The highest prevalence was detected in wolf (97.5%). Trichinella nativa was the most common species detected (98%). The diet of wolves was investigated by examining the stomach contents of 62 animals (75.6% of the total number of wolves examined for Trichinella). It consisted mainly of dog (36.4% of the total number of occurrences of all food items, PFO) and moose (31.2 PFO); however, during the hunting seasons of 1998–1999 and 1999–2000, skinned wolf carcasses were left in the forest as bait (567 carcasses, about 18,000 kg). This very high prevalence of Trichinella infection, the highest ever detected in a natural population of carnivores, could be explained by carnivore–carnivore transmission, influenced by the hunting practices adopted in the study area.

Trichinella Papuae and Trichinella Zimbabwensis Induce Infection in Experimentally Infected Varans, Caimans,Pythons and Turtles

The discovery of Trichinella zimbabwensis in farm crocodiles of Zimbabwe has opened up a new frontier in the epidemiology of the Trichinella genus. The objective of the present study was to investigate the infectivity of encapsulated species (T. spiralis, T. nativa, T. britovi, T. murrelli and T. nelsoni) and non-encapsulated species (T. pseudospiralis, T. papuae and T. zimbabwensis) in caimans (Caiman crocodilus), varans (Varanus exanthematicus), pythons (Python molurus bivittatus) and turtles (Pelomedusa subrufa) raised at their natural temperature range (26-32 degrees C). Mice and chickens were used as controls. At 6 days post-infection (p.i.), adult worms were detected in the small intestine of reptiles infected with T. papuae and T. zimbabwensis, of chickens infected with T. pseudospiralis and of mice infected with all encapsulated and non-encapsulated species. At 60 days p.i., T. papuae and T. zimbabwensis adult worms were collected from the intestine of varans and caimans and larvae from muscles of the four reptile species, T. pseudospiralis larvae from muscles of chickens, and larvae of all Trichinella species from mouse muscles. The highest reproductive capacity index of both T. papuae and T. zimbabwensis was observed in varans. The results show that T. papuae and T. zimbabwensis are able to complete their entire life-cycle in both poikilothermic and homoiothermic animals.

Echinococcus ortleppi and E. granulosus G1, G2 and G3 genotypes in Italian bovines

To increase the knowledge on Echinococcus genotypes infesting cattle and water buffaloes (Bubalus bubalis) born and bred in Italy, the germinal layer of hydatid cysts was collected from the liver and the lungs of 80 animals slaughtered in 2007. Two mitochondrial genes (the cytochrome c oxidase subunit I and the NADH subunit I) were tested by PCR. Four genotypes were identified: G1 (sheep strain), G2 (Tasmanian sheep strain), G3 (buffalo strain), and G5 (cattle strain). Fertile cysts were detected only in the lungs of 4.5% of the total G1 lung cysts, of 9.4% of the total G3 lung cysts, and in the only G5 infected animal. This is the first report of Echinococcus ortleppi (genotype G5) in Italy.

Molecular evidence of the camel strain (G6 genotype) of Echinococcus granulosus in humans from Turkana, Kenya

Cystic echinococcosis (CE) is a zoonotic helminthic disease, which is widely distributed throughout the world. Although G1 is the Echinococcus granulosus genotype most commonly involved in CE in humans, the prevalence of infection with other genotypes, such as G6, may be higher than previously thought. We performed molecular analysis to identify which E. granulosus genotypes are the causative agents of CE in humans in Kenyas Turkana district. During a Hydatid Control Programme in 1993-1994, 71 cyst fluid isolates of E. granulosus were collected during PAIR (puncture, aspiration, injection, re-aspiration) sessions. DNA was amplified for two genes from 59 isolates. Of these, 49 isolates (83%) were identified as G1 and 10 (17%) as G6. This is the highest prevalence of G6 detected in humans of the Old World, and our results suggest that, in highly contaminated environments, G6 might be of greater public health significance than previously believed.

Molecular identification of natural hybrids between Trichinella nativa and Trichinella T6 provides evidence of gene flow and ongoing genetic divergence

To date, there are no data available on the population genetics of Trichinella due to the lack of genetic markers and the difficulty of working with such small parasites. In the Arctic region of North America and along the Rocky Mountains, there exist two genotypes of Trichinella, Trichinella nativa and Trichinella T6, respectively, which are well differentiated by biochemical and molecular characters. However, both are resistant to freezing, show other common biological characters (e.g. low or no infectivity to rodents and swine) and produce fertile F1 offspring upon interbreeding. To data, these two genotypes have been considered allopatric. In this study, we detected both genotypes in wolves of the same wolf packs in Alaska, suggesting sympatry. A single GTT trinucleotide present in the ITS-2 sequence of T. nativa but not in Trichinella T6 was used as a genetic marker to study gene flow for this character in both a murine infection model and in larvae from naturally-infected Alaskan wolves. Only F1 larvae originating from a cross between T. nativa male and Trichinella T6 female were able to produce F2 offspring. Larvae (F1) originating from a cross between Trichinella T6 male and T. nativa female were not reproductively viable. As expected, all F1 larvae showed a heterozygote pattern for the GTT character upon heteroduplex analysis; however, within the F2 population, the number of observed heterozygotes (n=52) was substantially higher than expected (n=39.08), as supported by the F(is) index, and was not in the Hardy-Weinberg equilibrium. Larvae from two of the 16 Trichinella positive Alaskan wolves, showed the Trichinella T6 pattern or the T. nativa/Trichinella T6 hybrid pattern. Our data demonstrate that T. nativa and Trichinella T6 live in sympatry at least in Alaskan wolves, where T. nativa occurs more frequently (69%) than Trichinella T6 (31%). One explanation for this phenomenon is that glacial periods may have caused a geographical relocation, colonisation and independent evolution of T. nativa within the Rocky Mountains, resulting in a bifurcation of the freeze-resistant genotype. Additional studies will be required to test this hypothesis.

Spatial distribution and genetic diversity of Echinococcus multilocularis in Hungary

Human alveolar echinococcosis, caused by the tapeworm Echinococcus multilocularis, is the most pathogenic helminthic zoonosis in the temperate and arctic region of Europe. Between November 2008 and February 2009, 840 red fox (Vulpes vulpes) carcasses, were randomly collected from the whole Hungarian territory. The intestinal mucosa from all the foxes was tested by sedimentation and counting technique. E. multilocularis adult worms were detected in foxes of 16 out of the 19 Hungarian counties and in the suburban areas of the capital, Budapest. The prevalence and abundance of infection was significantly (P<0.001) higher in the north-western half (16.2%, CI=14.5-17.9; m ± SE=165.5 ± 112.4) than in the south-eastern half of the country (4.2%, CI=3.2-5.2; m ± SE=3.6 ± 2.1). The highest prevalence (26.6%, CI=22.5-30.8%) and abundance (m ± SE=614.2 ± 469.3) was observed in the Northern Mountain Region bordering Slovakia. The multi-locus microsatellite analysis of 81 worms showed the presence of four out of the five main European profiles. The H profile was the most common profile (55.5%) with nine genotypes, followed by the G (18.5%) with two genotypes, E (13.6%) with one genotype and D (12.4%) with two genotypes. The genetic distance was not statistically correlated with the geographical distance of the samples, supporting the hypothesis that the geographical distance is only a minor factor among those involved in the genetic distribution of this parasite in Europe. These data indicate that Hungary should be considered as a peripheral area of a single European focus, where the dispersal movement of foxes resulted in the spreading of the parasite from one county to another within a time period short enough to avoid a substantial genetic drift.

Echinococcus equinus and Echinococcus granulosus sensu stricto from the United Kingdom: genetic diversity and haplotypic variation.

Cystic echinococcosis is endemic in Europe including the United Kingdom. However, information on the molecular epidemiology of Echinococcus spp. from the United Kingdom is limited. Echinococcus isolates from intermediate and definitive animal hosts as well as from human cystic echinococcosis cases were analysed to determine species and genotypes within these hosts. Echinococcus equinus was identified from horse hydatid isolates, cysts retrieved from captive UK mammals and copro-DNA of foxhounds and farm dogs. Echinococcus granulosus sensu stricto (s.s.) was identified from hydatid cysts of sheep and cattle as well as in DNA extracted from farm dog and foxhound faecal samples, and from four human cystic echinococcosis isolates, including the first known molecular confirmation of E. granulosus s.s. infection in a Welsh sheep farmer. Low genetic variability for E. equinus from various hosts and from different geographical locations was detected using the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), indicating the presence of a dominant haplotype (EQUK01). In contrast, greater haplotypic variation was observed for E. granulosus s.s. cox1 sequences. The haplotype network showed a star-shaped network with a centrally placed main haplotype (EgUK01) that had been reported from other world regions.