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PubMed2006

The relationship between the rate of molecular evolution and the rate of genome rearrangement in animal mitochondrial genomes.

Evolution of mitochondrial genes is far from clock-like. The substitution rate varies considerably between species, and there are many species that have a significantly increased rate with respect to their close relatives. There is also considerable variation among species in the rate of gene order rearrangement. Using a set of 55 complete arthropod mitochondrial genomes, we estimate the evolutionary distance from the common ancestor to each species using protein sequences, tRNA sequences, and breakpoint distances (a measure of the degree of genome rearrangement). All these distance measures are correlated. We use relative rate tests to compare pairs of related species in several animal phyla. In the majority of cases, the species with the more highly rearranged genome also has a significantly higher rate of sequence evolution. Species with higher amino acid substitution rates in mitochondria also have more variable amino acid composition in response to mutation pressure. We discuss the possible causes of variation in rates of sequence evolution and gene rearrangement among species and the possible reasons for the observed correlation between the two rates.

Amino Acids↗
PubMed2002

Phylogenetic analysis of bacterial communities associated with ectoparasitic chewing lice of pocket gophers: a culture-independent approach.

This study identifies the bacteria associated with ectoparasitic chewing lice that live in the fur of pocket gophers. Samples of chewing lice were collected from pocket gopher hosts in Florida, Missouri, New Mexico, and Costa Rica. We used a molecular sampling method whereby total community DNA was extracted from samples of chewing lice, and PCR was used to selectively amplify small-subunit rRNA genes from bacteria. This culture-independent method yielded ca. 35 distinct lineages representing eight widely divergent groups within the domain Bacteria. Phylogenetic analysis of two lineages (Acinetobacter and Staphylococcus) provides evidence that multiple species of each group are found in chewing lice. Phylogenetic analysis also demonstrated that diversification within chewing lice may be evident in both Acinetobacter and Staphylococcus. Some clones amplified from chewing louse hosts appeared to be distinct from known species of Acinetobacter and Staphylococcus. This diversification may be the result of the extreme isolation of populations of both chewing lice and their pocket gopher hosts.

Animals↗
PubMed2002

Light and scanning electron microscopical study on Antarctophthirus ogmorhini lice from the Antarctic seal Leptonychotes weddellii.

Adult lice (Antarctophthirus ogmorhini) from the Weddell seal Leptonychotes weddellii were investigated by means of light and scanning electron microscopy. We established that this species is characterized by several morphological peculiarities which enable it to survive the low temperatures of the Antarctic sea and the body depression which occurs during the deep (450 m) and long diving periods of the seals. The main peculiarities are: (1) the cuticle of the ventral and lateral surfaces is much thinner than that of the dorsal surface, (2) the body has numerous stiff spines which are covered by a thick layer of the seal's sebum that closely surrounds the body of the louse, (3) the whole body is covered by a close layer of leaf-like scales which are apparently able to trap air bubbles and thus to provide a small zone of air close to the surface of the cuticle.

Animals↗
PubMed2002

A survey of bacterial diversity in ticks, lice and fleas from Australia.

We isolated bacteria from ticks, lice and fleas. Partial small subunit rRNA sequences were obtained for each isolate and the closest matches in the FastA database were determined. These bacteria were mostly Gram-positive (Firmicutes), although representatives from the Proteobacteria (alpha, beta, gamma subdivisions) and CFB group were also isolated. Most of the isolates we found were from genera that were present in most of the ectoparasites studied, but a few genera were restricted to one species of ectoparasite. The most commonly isolated genera were Stenotrophomonas, Staphylococcus, Pseudomonas, Acinetobacter and Bacillus. Species of Bacillus and Proteus, which have biopesticide potential, were found in some of these ectoparasites. Overall, the communities of bacteria were similar to those found in other studies of parasitic arthropods.

Animals↗
PubMed2004

Comparative survey of the ectoparasite fauna of wild and farm-reared red-legged partridges ( Alectoris rufa), with an ecological study in wild populations.

We compared the ectoparasite fauna of 89 wild red-legged partridges (Alectoris rufa) from four hunting estates and 25 farm-reared partridges from three farms. We found 62% of the wild but only 20% of the farmed partridges harboured ectoparasites. On the wild partridges, one hippoboscid fly species (Ornithophila metallica, 2%), two tick species (Ixodes frontalis, 2%; Hyalomma sp., 17%) and eight louse species were found (Menacanthus lyali, 3%; M. numidae, 3%; Menopon pallens, 21%; Myrsidea picae, 1%; Goniocotes obscurus, 17%; G. simillimus, 1%; Goniodes dispar, 35%; Cuclotogaster obscurior, 28%). Only two louse species (G. obscurus, 8%; C. obscurior, 20%) were found on farmed partridges. Lice prevalence, abundance and species richness were higher in wild birds (44%, 17.0, 1.1) than in farmed partridges (20%, 1.3, 0.3). Lice prevalence and abundance were higher in dead-found (54%, 21.6) than in shot (23%, 2.3) or live-trapped wild partridges (no lice). Tick prevalence and abundance was higher in live-trapped (100%, 1.14) than in dead-found (13%, 0.5) or shot partridges (7%, 0.1). In dead-found partridges, the total louse prevalence and abundance, the number of louse species and the abundance of G. dispar, G. obscurus, C. obscurior and M. pallens were negatively correlated with partridge body condition; and this correlation for G. dispar abundance was more pronounced in juveniles than in adult partridges. Since juvenile individuals were also more parasitised by C. obscurior and Hyalomma sp., an acquired immunity against arthropods seems to be relevant. Released partridges are not a source of new ectoparasites, but these birds may come into contact with many arthropod species with which they had no previous contact.

Animals↗
PubMed2004

Natural infestation of the chewing lice (Werneckiella equi) on horses and treatment with imidacloprid and phoxim.

Infestation with the chewing louse (Werneckiella (Damalinia) equi) can be found on horses world-wide. Louse infestations, including clinical signs of louse-derived dermatitis, are known from Icelandic horses. A clinical field investigation was conducted in Iceland using horses with natural louse infestations to evaluate the efficacy of imidacloprid in a 10% solution in comparison with phoxim in a 0.05% solution. A total of 27 horses received a single imidacloprid treatment using 16 ml of the 10% solution along the mane and on the dorso-lateral trunk. A further 43 horses were treated twice, 14 days apart, with phoxim, using 2 x 50 ml solution applied along the mane and the dorso-lateral trunk. At the final evaluation on day 28, complete control of the lice was obtained for the imidacloprid treated horses and only a single moribund louse was found on two horses treated with phoxim.

Animals↗
PubMed2005

Dermatological and parasitological evaluation of infestations with chewing lice (Werneckiella equi) on horses and treatment using imidacloprid.

Lice infestations in horses caused by the chewing louse Werneckiella (Damalinia) equi are observed worldwide. In the present study, the efficacy of 10% imidacloprid was tested on horses naturally infested with lice. Two groups of animals received a double application of 4 ml and 8 ml Advantage 10% spot-on on day 0 and 28 either. Horses, presenting dermatological signs with negative lice counts, were also included in this investigation. 40.86% of the horses presented positive lice counts and 84.21% of these animals showed clinical dermatologic signs. 65.45% of the lice-negative horses also showed clinical manifestations. Two days after treatment, lice counts dropped in both the treatment groups and on day 56, all animals were free of alive lice, and dermatological lesions decreased significantly (P<0.001) in both the lice-positive and the negative animals. No correlation (P>0.050) between lice burden and clinical signs was detected.

Animals↗
PubMed2005

Infestation of Werneckiella equi on Icelandic horses, characteristics of predilection sites and lice dermatitis.

Lice infestations on horses caused by the lice Werneckiella (Damalinia) equi and Haematopinus equi are observed worldwide. In this study, the distribution and clinical manifestations of lice on Icelandic horses were examined. Thirty-eight out of 93 animals (40.86%) were identified as infested with W. equi. Sixty-eight animals (73.12%) presented dermatological lesions associated with lice infestation, while only 32 of these animals presented lice. Six animals had no clinical signs although of being lice-positive, and 19 animals (20.43%) showed neither lice nor clinical manifestations. Lice burdens varied from animal to animal, and clinical manifestations occurred at all levels of infestation. Focal alopecia was the main clinical sign (83.78%) on lice-positive horses, while scaling and crusts occurred in 10.81% and 9.68% of the cases, respectively. Clinical signs present in the head and the neck/mane area were found to be an indication of lice infestation in horses.

Animals↗
PubMed2006

A new shampoo based on neem (Azadirachta indica) is highly effective against head lice in vitro.

Because topical compounds based on insecticidal chemicals are the mainstay of head lice treatment, but resistance is increasing, alternatives, such as herbs and oils are being sold to treat head lice. To test a commercial shampoo based on seed extract of Azadirachta indica (neem tree) for its in vitro effect, head lice (n=17) were collected from school children in Australia and immersed in Wash-Away Louse shampoo (Alpha-Biocare GmbH, Germany). Vitality was evaluated for more than 3 h by examination under a dissecting microscope. Positive and negative controls were a commercially available head lice treatment containing permethrin 1% (n=19) and no treatment (n=14). All lice treated with the neem shampoo did not show any vital signs from the initial examination after immersion at 5-30 min; after 3 h, only a single louse showed minor signs of life, indicated by gut movements, a mortality of 94%. In the permethrin group, mortality was 20% at 5 min, 50% at 15 min, and 74% after 3 h. All 14 head lice of the negative control group survived during the observation period. Our data show that Wash-Away Louse is highly effective in vitro against head lice. The neem shampoo was more effective than the permethrin-based product. We speculate that complex plant-based compounds will replace the well-defined chemical pediculicides if resistance to the commonly used products further increases.

Animals↗
PubMed1999

The possibility of testing antiparasitical substances using the cockroach as a model.

Products used against parasitic arthropods must be tested for their efficacy. Because the supply of parasitic organisms for such tests may be a limiting factor, it is best to conduct these tests with a model organism. We show that the cockroach is a suitable model organism because it is easy to keep and to breed. Moreover, all stages of these animals are more resistant than, or at least as resistant as, the corresponding parasites, so the results with cockroaches can also be taken as valid for ectoparasites.

Animals↗