Babesiosis

Babesiosis is the disease caused by infection of the erythrocytes of mammals by Babesia species, which are Apicomplexa protozoa belonging to the suborder Piroplasmidea and the family Babesiidae. They are different from the Theileriidae, which can also infect white blood cells and endothelial cells. Babesiosis is one of the most important tick-borne infectious diseases of domestic and wild mammals and still poses significant diagnostic and therapeutic challenges for veterinary practitioners around the world. It is an increasing problem worldwide because of the expansion of tick habitats and the increased mobility of animals, which promote the spread of parasites into new geographical areas. Babesia species can, exceptionally, infect humans, especially splenectomised or immunocompromised individuals. The majority of human cases involve B. microti, a parasite of rodents, but human infections may also be caused by B. divergens, which infects cattle, or by Babesia related to B. odocoilei, which infect cervids. The majority of new developments, in regard to taxonomy, epidemiology, pathogenesis and control, concern canine babesiosis, whereas piroplasmosis in horses or cattle retains the classical description, therefore the focus of this article will be on infection in dogs.

Use of a mathematical model to study the dynamics ofCtenocephalides felispopulations in the home environment and the impact of various control measures

The biology of fleas has been studied by a number of authors, as has the impact of various types of control measures. However, there are no mathematical models simulating the dynamics of a population of Ctenocephalides felis felis fleas on their host (the cat) and in their close environment (apartment). The model presented in this paper allows for integration of the numerous biological and behavioural parameters of the parasites and their hosts and for the variation of these same parameters. The various types of control measures can be programmed so that their impact over time can be studied. The model confirms the key role played by adult fleas, or emerged fleas contained in the cocoon. Only regular applications of persistent insecticides to the host animal will enable control of the parasite population. A combination of these insecticides with an IGR (Insect Growth Regulator) will accelerate decontamination of the home environment and see the disappearance of the parasites altogether if they are not reintroduced. The association of additional measures such as vacuum cleaning will accelerate the process of decontamination but will have no impact if carried out in isolation. One-off treatment with insecticide will not enable a reduction in the parasite population, even if carried out frequently. Use of insecticides on the home environment premises alone does not appear to be an adequate means of control. The present model can be used to test various integrated control measures which take into account different factors such as the number of host animals, the frequency of movement outdoors, the impact of the seasons.

American Association of Veterinary Parasitologists' review of veterinary fecal flotation methods and factors influencing their accuracy and use--is there really one best technique?

The principle of fecal flotation is based on the ability of a solution to allow less dense material (including parasite elements) to rise to the top. However, there are numerous factors that will influence the accuracy and use of such a theoretically simple technique. Whether or not centrifugation is used appears to have an impact on the ability to detect some parasites, but not others. Using a flotation solution with a relatively high specific gravity favors the simultaneous flotation of the diagnostic stages of many different parasites while, at the same time, making recognition of some more difficult because of distortion as well as the amount of debris in the preparation. Dilution methods tend to be less accurate because they require extrapolation; however, they are quicker to perform, in part, because of the cleaner preparation. Timing is a critical factor in the success of all flotation methods, as is technical ability of the personnel involved. Thus, simplicity, low costs and time savings have generally favored gravitational flotation techniques (including the McMaster technique and its modifications). How accurate the method needs to be is dependent upon the purpose of its use and choice of method requires an understanding of analytical sensitivity and expected levels of egg excretion. In some instances where the difference between, for example, 0 and 50 eggs per gram is insignificant with regards to management decisions, less accurate methods will suffice. In others, where the presence of a parasite means treatment of the animal regardless of the numbers of eggs present, methods with higher analytical sensitivities will be required, particularly for those parasites that pass few eggs. For other uses, such as the Fecal Egg Count Reduction Test, accuracy may become critical. Therefore, even though recommendations for standardized fecal flotation procedures have been promoted in the past, it is clear that the factors are too numerous to allow for the recommendation of one, or even a few, procedures for all purposes.

New method using quantitative PCR to follow the tick blood meal and to assess the anti-feeding effect of topical acaricide against Rhipicephalus sanguineus on dogs

A 28-day study was conducted to assess the dynamic of blood feeding by Rhipicephalus sanguineus ticks on dogs treated or not with a novel topical combination of fipronil, amitraz and (S)-methoprene. Dogs were infested weekly through exposure to ticks in crates for 4h. Ticks were then counted in the crates at 2h and 4h post dog exposure. Ticks were also counted and removed from the dogs at 2h, 4h, 6h, 12h and 24h post tick exposure. The inhibition of blood feeding was assessed by both tick quantification and designing and performing a quantitative PCR (qPCR) to detect the canine hydroxymethylbilane synthase (HMBS) gene in ticks. The percentage of repellency sensu lato based on the ticks collected in crates at 2h varied from 4.7% at day 28 to 48.3% at day 7. The immediate mortality rate of the ticks expelled at 2h varied from 1.5% at day 21 to 31.7% at day 7. The efficacy calculation showed that the acaricidal combination started to kill ticks in as little as 2h. The average efficacy reached 90.0% at 12h post crate challenges and 100% at 24h post exposure in crates. The inclusion of an internal amplification control was used to ensure that no significant template-derived PCR inhibition (≤ 6.2%) affected the overall results. The reduction of blood feeding was significant at 4h (>80.0%) and >99.0% at 24h post tick exposure in the crate. The high repellency rate and the lethal efficacy of CERTIFECT(®) resulted in significantly fewer live attached ticks, consequently reducing blood intake and fluid exchanges.

Epidemiological survey of anti-flea IgE in dogs in Japan by using an antigen-specific IgE quantitative measurement method

In Japan, an epidemiological survey was performed in dogs from October to December 2008 by using a quantitative measurement method for antigen-specific IgE towards specific Ctenocephalides felis antigens. 214 dogs from 22 veterinary clinics were included. These clinics were located as follows, from North to South: Hokkaido, Aomori, Fukushima, Tochigi, Saitama, Chiba, Tokyo (Tama-City and Ota-ku), Kanagawa, Gifu, Niigata, Kyoto, Nara, Osaka, Hyogo, Kagawa, Ehime, Hiroshima, Yamaguchi, Fukuoka, Kumamoto and Kagoshima. 110 dogs (51.4%) were seropositive for flea-specific IgE. No differences were associated with gender or breed. This survey confirms that flea infestation in dogs is a common problem in Japan. It especially shows that the infestation also occurs in Northern Japan where fleas are considered uncommon by the vet.

Comparative efficacy on dogs of a single topical treatment with fipronil/(S)-methoprene or weekly physiological hygiene shampoos against Ctenocephalides felis in a simulated flea-infested environment

Flea infestations of pets continue to persist due to the lack of knowledge of flea biology and ecology. It is not unusual that pet owners believe regular hygiene, such as shampooing their dogs can replace regular insecticidal treatment. The objective of this study was to compare in a flea simulated environment, modelling exposure similar to that found in a home, that the use of regular physiological shampoo does not control fleas adequately when compared to a long acting topical formulation. Three groups of six dogs were formed: one untreated control group, one group treated monthly with the topical formulation of fipronil/(S)-methoprene, and a third group treated weekly with a hygiene shampoo. All dogs were infested with adult unfed Ctenocephalides felis fleas (200 ± 5) on Days -28 and -21. Each animal’s sleeping box was fitted with a plastic cup mounted to the inside roof of the box. The sleeping bench of each animal was covered with a carpet to accommodate flea development. The dogs were maintained in their kennels throughout the study. In order to maintain the environmental flea challenge, C. felis pupae (100 ± 5) were placed in the plastic cup in each animal’s sleeping box on Days -14, -7, 0, 7, 14, 21, 28, 35 and 42. The dogs were combed and fleas counted weekly on Days -1, 3, 10, 17, 24, 31, 38, 45, and 51. The fleas were placed immediately back on the dogs. On Day 60, fleas were counted and removed. Flea infestations in the untreated control group at each count averaged between 46.2 and 74.2 fleas throughout the study. The average number of fleas infesting dogs was significantly different (p < 0.05) between the untreated and the two treatment groups and between the two treatment groups at all counts throughout the two months study (Days 3, 10, 17, 24, 31, 38, 45, 51 and 60). The efficacy was never below 99.1% in the fipronil/(S)-methoprene group, and efficacy in the shampoo group was never above 79.2%. Weekly shampooing in treatment group 3 was intentionally delayed after Day 42, to evaluate wether missing a weekly bath would affect the flea population. The Day 48 data indicate that forgetting or delaying a single weekly shampooing resulted in a clear increase in flea numbers and a significant decrease in efficacy from 68.2% to 34.8%. The fipronil(S)/methoprene treatment allowed a continuous control as demonstrated by the high efficacy against fleas, and also the number of flea-free dogs on seven of the nine weekly assessments, in spite of what was essentially a continuous flea challenge model.

Study of the sustained speed of kill of the combination of fipronil/amitraz/(S)-methoprene and the combination of imidacloprid/permethrin against Dermacentor reticulatus, the European dog tick

The sustained speed of kill against Dermacentor reticulatus of two topical combinations, one containing fipronil/amitraz/(S)-methoprene and the other, imidacloprid/permethrin, was evaluated in dogs. Two treated groups and one untreated control group of eight adult Beagle dogs each were randomly formed based on pre-infestation rates and bodyweight. Each treatment was administered topically once on Day 0, according to the recommended label dose and instructions for use. All dogs were infested with 50 adult unfed D. reticulatus starting on Day 1, then weekly, for a total of five weeks. While most studies determine tick efficacy at 48 hours (h), in this study, all remaining ticks were counted and categorized 24 h following each infestation. The numbers of ticks (living or dead) that remained attached on treated dogs were compared to those on the control animals. The percent reduction of attached ticks (disruption of attachment) at 24 h on dogs treated with fipronil/amitraz/(S)-methoprene remained above 92% for four weeks. The reduction of attached ticks at 24 h on dogs treated with imidacloprid/permethrin did not reach 80% during the entire study. The number of ticks attached at 24 h was significantly (p < 0.05) lower in the fipronil/ amitraz/(S)-methoprene group than in the imidacloprid/permethrin group in assessments on Days 2, 15, 22, 29 and 36. When assessing efficacy based upon live ticks on treated versus control dogs, fipronil/amitraz/(S)-methoprene 24 h efficacy was above 95% for four weeks, decreasing to 77.8% at Day 36. The 24 h efficacy of imidacloprid/permethrin ranged from 56.2% to 86.7% through Day 29, never achieving 90% throughout the study. The 24-hour efficacy of fipronil/amitraz/(S)-methoprene was significantly (p < 0.05) higher than imidacloprid/permethrin at all time points, including Day 36.

Comparative efficacy on dogs of a single topical treatment with the pioneer fipronil/(S)-methoprene and an oral treatment with spinosad against Ctenocephalides felis

In the study reported here, the pioneer fipronil/(S)-methoprene topical product (FRONTLINE^® PLUS, Merial Limited, Duluth, GA) was compared to the oral spinosad product (COMFORTIS^® Elanco, Greenfield, IN) for efficacy against adult fleas and preventing egg production. The product presentations, doses and labelling were the one applicable in the USA. Using a standard protocol, 200 cat fleas of mixed sex were applied to dogs on Days 1, 7, 14, 21, 28, 35, and 42. Dogs were combed to remove fleas 24 hours post-infestation, the fleas were counted, collected, and then reapplied to each dog following completion of their respective count. At 48 hours post-infestation, comb counts were performed and fleas were removed. No fleas were collected from any dog in the fipronil/(S)-methoprene group at any 24 or 48 hours post-infestation assessment throughout the six weeks study, yielding a preventive efficacy of 100%. For the spinosad treatment, efficacy was 100% at 24 hours and 48 hours through Day 16, and thereafter declined. The results observed in the spinosad-treated dogs were highly variable between animals. At the 24 and 48 hours counts following the Day 21 infestation, only five of eight spinosad-treated dogs (62.5%) were flea-free. Following the Day 28 infestation, spinosad efficacy fell to 85% and 89%, for the 24 hours and 48 hours counts, and only two dogs (25%) were flea free, compared to 100% flea-free dogs in the fipronil/(S)-methoprene group. No fleas were collected from the fipronil/(S)- methoprene treated dogs throughout the entire study, therefore, no eggs were collected at any time from any dog in the group. However, in the spinosad group adult fleas were found on dogs starting on Day 21 and by Day 30, 42 eggs were collected from one dog that had 107 adult fleas counted at 48 hours. At Day 37 and Day 49, more than 100 eggs were collected from each dog in the spinosad-treated and control groups.

Defining the concept of 'tick repellency' in veterinary medicine

Although widely used, the term repellency needs to be employed with care when applied to ticks and other periodic or permanent ectoparasites. Repellency has classically been used to describe the effects of a substance that causes a flying arthropod to make oriented movements away from its source. However, for crawling arthropods such as ticks, the term commonly subsumes a range of effects that include arthropod irritation and consequent avoiding or leaving the host, failing to attach, to bite, or to feed. The objective of the present article is to highlight the need for clarity, to propose consensus descriptions and methods for the evaluation of various effects on ticks caused by chemical substances.

Results of a European multicentric field efficacy study of fipronil-(S) methoprene combination on flea infestation of dogs and cats during 2009 summer

Despite the increasing number of ectoparasiticides for pets and their use, flea infestations of cats and dogs are still widespread in Europe. It is therefore important to assess the maintenance of efficacy of the ectoparasiticides for cats and dogs. The present studies aimed to evaluate the efficacy of monthly treatments using a fipronil/(S)-methoprene combination spot-on (Frontline Combo) on dogs and cats from private veterinary clinics located in seven European countries. The survey was conducted for three months during the flea season 2009. A total of 233 dogs and 180 cats were included. Each animal was treated at Days 0 (Day 0), 30 (D30) and 60 (D60) at the vet clinics. For each animal, at least three flea counts were performed at D0, D30 and/or D60 and/or day 90 (Day 90) in order to evaluate the prevalence of flea infestation and the efficacy of control. At the beginning of the study the prevalence of infested animals was 41.63% (97/233) in dogs and 47.22% (85/180) in cats. At D90, the number of dogs remaining infested fell to 8/211 therefore 91.75% became flea-free. The number of infested cats fell from 85 to 9/173 at D90 therefore 89.41% were cured. All animals still infested at Day 90 were living under epidemiological conditions that favour heavy flea burdens. These results are similar or better to previous studies, indicating the continuous high level of efficacy for fipronil 10 years after launch.

Prevalence of flea infestation in dogs and cats in Hungary combined with a survey of owner awareness

A survey was conducted in order to gain current information on flea species (Siphonaptera: Pulicidae) infesting dogs and cats living in urban and rural areas of Hungary, along with data on the factors that affect the presence, distribution and seasonality of infestation. In addition, owner awareness of flea infestation was evaluated. Practitioners in 13 veterinary clinics were asked to examine all dogs and cats attending the clinic and to collect fleas, when present, on 2 days in each month from December 2005 to November 2006. They also completed a questionnaire for each animal examined. A total of 319 dogs (14.1%) were found to be infested; the highest prevalence (27.1%) of infestation on dogs occurred in August and the lowest (5.4%) in May. Prevalence of fleas on cats was higher (22.9%); the highest (35.0%) and lowest (8.1%) prevalences occurred in July and April, respectively. Fleas were more prevalent in rural (387/1924 animals, 20.2%) than in urban (161/1343 animals, 12.0%) areas. Three species, Ctenocephalides felis (Bouché), Ctenocephalides canis (Curtis) and Pulex irritans L., were found. On dogs, the prevalence of C. canis alone was 53.0%, whereas that of C. felis alone was 36.0%. Only 19 specimens of P. irritans were found on 14 dogs from rural habitats only. Prevalence of C. felis only on cats was 94.3%; the remaining cats were infested with either C. canis or with mixed infestations of C. felis and C. canis. More than half (51.4%) of the owners of infested dogs and cats had not used flea control products in the past year or more, and five times as many owners in rural than urban areas had not used flea control products in the same period. Very few owners reported having attempted to kill fleas in their animals' environment; instead, they believed that fleas were acquired from other cats or dogs.

A comparative evaluation of the speed of kill and duration of efficacy against weekly infestations with fleas on cats treated with fipronil-(S)-methoprene or metaflumizone

Spot-on formulations of metaflumizone and a combination of fipronil-(S)-methoprene were evaluated in adult cats to determine the duration of 24- and 48-hour efficacy and short-term speed of kill against adult cat fleas, Ctenocephalides felis felis. Speed of kill efficacies (at 12, 18, 24, and 48 hours) were assessed against existing (day -1) infestations and against infestations at day 7, and efficacy was assessed 24 and 48 hours after weekly flea infestations through day 42. Cats treated with fipronil-(S)-methoprene had significantly (P<.01) fewer fleas than those treated with metaflumizone at 12 and 18 hours after treatment (day 0) and on the day 7 infestations. Fipronil-(S)-methoprene-treated cats also had significantly (P<.05) fewer fleas than metaflumizone-treated cats for all 24-hour counts from initial treatment on day 0 through infestation day 42 and for the 48-hour counts on day 28 through day 42.

Survey of flea infestation in dogs and cats in the United Kingdom during 2005

During 2005, 31 uk veterinary practices participated in a survey of flea infestation, during which 2653 dogs and 1508 cats were examined for evidence of flea infestation and skin disease compatible with flea allergy dermatitis (fad). The prevalence of flea infestation in the cats was 21.09 per cent, significantly (P<0.001) higher than in the dogs (6.82 per cent). The prevalence of skin lesions compatible with fad in the cats (8.02 per cent) was also significantly (P<0.001) higher than in the dogs (3.32 per cent). Flea infestations were more common in households with cats and with more than one pet. Of 467 fleas identified from the cats, 462 (98.93 per cent) were Ctenocephalides felis, one was Ctenocephalides canis, one was Archaeopsylla erinacei, two were Pulex irritans, and one was Spilopsyllus cuniculi. Of 336 fleas identified from the dogs, 313 (93.15 per cent) were C felis, five were C Canis, 12 were A erinacei, five were P irritans, and one was Ceratophyllus (Nosophyllus) fasciatus. Almost half of the owners of the dogs and cats were unaware of their pet's flea infestation. The overall prevalence of fleas and/or skin lesions that could potentially be compatible with fad was 7.46 per cent in the dogs and 22.28 per cent in the cats.

Efficacy of fipronil-(S)-methoprene on fleas, flea egg collection, and flea egg development following transplantation of gravid fleas onto treated cats

The goal of this study was to assess the insect growth regulator activity of the combination product fipronil-(S)-methoprene under a severe challenge model. Gravid fleas were allowed to feed on untreated donor cats for 48 hours before being transplanted onto untreated control cats and treated cats (treated once on day 0); 24 hours later, adult fleas were collected from all cats and counted to assess the 24-hour kill efficacy against the transplanted fleas, and flea eggs were collected and incubated to assess viability. The process was repeated weekly for 11 weeks. The 24-hour efficacy against transplanted adult fleas in the treated group was about 100% for the first 3 weeks and gradually declined to 93.4% by week 6. Egg production numbers were reduced on the treated cats compared with controls, with geometric mean egg counts on treated cats reduced from 76.9% to 96.3% during the initial 6 weeks of the study. The combination product was 100% ovicidal through day 56 and was still about 98% effective against eggs at the end of the study (day 76).

Comparative efficacy of the combination fipronil-(S)-methoprene and the combination permethrin-imidacloprid against Dermacentor reticulatus, the European dog tick, applied topically to dogs

This study compared the efficacy of two of the most widely veterinary-dispensed topical products for control of ticks on dogs: fipronil-(S)-methoprene and imidacloprid-permethrin. Eighteen healthy beagle dogs of both sexes were divided into three groups of six dogs. Group 1 served as the untreated control. Dogs in group 2 were treated with fipronil 10% + (S)-methoprene 9% w/v applied once on day 0, and those in group 3 were treated with imidacloprid 8.8% and permethrin 44% w/v, applied once on day 0. All dogs were infested with approximately 50 unfed Dermacentor reticulatus ticks on days 1, 7, 14, 21, 28, 35, and 42, and ticks remaining were counted and removed 48 hours after each infestation. The 48-hour efficacy of the fipronil-(S)-methoprene combination remained at 100% at all assessment points through and including day 37, declining to 95.30% on day 44. The 48-hour efficacy of the imidacloprid-permethrin combination peaked at 86.46% on day 9, decreased to 73.37% by the third week, and fell to 63.53% by the end of the study (day 44). Significantly (P < .05) fewer ticks were recovered from dogs treated with fipronil-(S)-methoprene or imidacloprid-permethrin than from untreated control dogs at each infestation. Notably, the dogs treated with fipronil-(S)-methoprene had significantly (P < .05) lower tick counts at every assessment than the dogs treated with imidacloprid-permethrin.

Assay of fipronil efficacy to prevent canine monocytic ehrlichiosis in endemic areas

Our objective was to evaluate the efficacy of fipronil for the prevention of Ehrlichia canis transmission to dogs by Rhipicephalus sanguineus in two endemic areas situated in Africa (Dakar and Djibouti). We carried out controlled trials in kennels for 1 year on 248 dogs, mainly police dogs and military working dogs. Eight groups were studied in a multi-centre study. Fifty five fipronil treated dogs were located in two separated kennels (G3, 37 dogs in Djibouti and G8, 18 dogs in Dakar). G1 (66 dogs) and G2 (60 dogs) were untreated control groups located in Djibouti, whereas G4 (32 dogs), G5 (13 dogs), G6 (18 dogs) and G7 (4 dogs) were the control groups located in Dakar. The epidemiological status of each group is known. G1 and G2 dogs were not kept in kennels, whereas G3, G4, G5, G6, G7, G8 dogs were housed in equivalent kennels. Tick infestation, clinical status and Ehrlichia seroprevalence were assessed during 1 year (duration of the study). Dog treated with fipronil showed neither canine monocytic ehrlichiosis (CME) nor tick infestations. In all groups of untreated control animals, R. sanguineus tick infestations were frequent, particularly in kennels (G5, G6 and G7) as well as morbidity and mortality due to CME. E. canis infection rates were low for fipronil treated animals: 2.7% (1/37) for G3 and 5.5% (1/18) for G8 group. Among control animals, seroprevalence was maximum (100%) in dogs kept in kennels (G5, G6 and G7 groups) and high among native dogs in Djibouti (G1 group): 69.7% (46/66) and in Dakar (G4 group): 50% (16/32). Dogs belonging to expatriate citizens (G2 group) were less likely to be infected: 21.7% (13/60). The comparison of serological results among French army dogs and French citizen dogs that were introduced in Djibouti for an average of 10 months shows a statistically significant (P<0.001) difference. Among fipronil treated animals (G3 group), 2 dogs out of 55 seroconverted (3.6%) compared to 13 out of 60 dogs (21.7%) in the control G2 group. The results of our study indicate the preventative efficacy of a fipronil monthly treatment to avoid CME in endemic areas. Epidemiological data concerning animals that live in the same endemic areas are an example of the serious consequences (in terms of mortality and morbidity) that are related to the absence of efficient methods for tick-control. In order to protect dogs that are in transit in endemic areas against tick-transmitted diseases, the use of an adapted acaricide product is recommended.

Efficacy of oxfendazole for the treatment of giardiosis in dogs. Experiments in dog breeding kennels

Giardiosis is one of the most frequent parasites of dogs and cats. Since several years, the treatment is based on the use of metronidazole. A coproscopic study in four dog kennels was conducted to demonstrate, at a significant level, the efficacy of oxfendazole (Dolthène, Merial). At the posology of 11.3 mg/kg each day during three days (D1, D2 and D3), no dogs eliminated Giardia cysts and all dogs are clinically cured. The importance of hygienic measures is underlined. In kennels 1 and 2 where hygienic conditions were poor, dogs reexcreted cysts again after treatment. In kennels where the boxes were disinfected, no dogs, treated with 22.6 or 11.3 mg/kg, reexcreted Giardia cysts.

Use of a mathematical model to study the control measures of the cattle tick Boophilus microplus population in New Caledonia

Boophilus microplus is a common cattle tick of great economic importance in various tropical and subtropical countries like New Caledonia. The proposed model describes the population dynamics of female Boophilus microplus in the absence of resistant ticks. It is a system of six difference equations which can be mathematically analyzed. The analysis of the system shows the great importance of the eigenvalue denoted by lambda1. The population of ticks increases if lambda1 < 1 and decreases if lambda1 > 1. The lambda1 eigenvalue depends, in particular, on the parasitic surviving rate and encounter rate between the larvae and the cows. The treatments decrease the parasitic surviving rate as the agronomic measures decrease the encounter rate. This model permits to quantify the conditions of treatments (or of the efficacy of a vaccine) and of agronomic measures by which the populations are controlled. It shows that the different treatment rhythms and the presence or not of the wild or domestic refuges plays a major role on the dynamics of tick population.

Resistance of the red poultry mite to pyrethroids in France

The resistance of Dermanyssus gallinae, the red poultry mite, to a pyrethroid acaricide, permethrin, and to an organophosphate, dichlorvos, was examined on five French poultry farms which had experienced problems in controlling mite populations and on one farm with no problems. The concentration of permethrin required to kill 50 per cent of the mites on the five farms was between eight and 40 times the concentration required on the control farm. In contrast, no resistance to dichlorvos was detected. This is the first description of resistance to a pyrethroid in D gallinae in France.

[Two cases of hepatic helminthiasis in Marmota monax with hepatitis virus(WHV) infection]

Autopsy of two Woodchuck Hepatitis Virus (WHV) infected Woodchucks, Marmota monax, revealed the presence of two parasites in an hepatic localization, Taenia mustelae (Larvae) and Calodium hepaticum. The authors present the identification of the two parasites, based on the observation of cysticerci of Taenia mustelae, or on the observation of the eggs of C. hepaticum. They discuss the probable interaction between hepatic parasites and WHV infection.

Use of free living stages to study the effects of thiabendazole, levamisole, pyrantel and ivermectin on the fine structure of Haemonchus contortus and Heligmosomoides polygyrus

Ultrastructural changes induced in vitro by thiabendazole, levamisole, pyrantel and ivermectin in the free living larval stages of two trichostrongyles (Heligmosomoides polygyrus and Haemonchus contortus) were analysed. The observed damage for each anthelmintic is related to the known mode of action and compared to the damage commonly described in adults. The advantage of using larvae to study the effects of anthelmintics on the fine structure of nematodes rather than adults is described. Thiabendazole induced alteration of the cellular organization especially epithelial cells of the digestive tract. Changes in mitochondria were also seen. Levamisole caused contraction of muscle fibres whereas no specific lesions were observed with pyrantel. Ivermectin caused an hypertrophy of muscular groups. The interest of such a technique in research on the modes of action of anthelmintics is emphasized.

Tick resistance to pyrethroids in New Caledonia

Boophilus microplus is the common cattle tick of great economic importance in New Caledonia. Since 1986, deltamethrin has been used for dipping. In 1992, an increase of tick infestations was seen on some ranches. Field and laboratory studies were conducted to determine if resistant ticks were present. Ticks resistant to deltamethrin were detected on three ranches, with resistance factors from 8.3 to 97.7. All deltamethrin-resistant isolates were also resistant to fenvalerate, but only one was also resistant to flumethrin. The combination of deltamethrin and ethion seemed to be active on isolates. This is the second description of isolates of Boophilus microplus resistant to pyrethroids, the first being in Australia and points to future problems in the management of tick control. Some organophosphates like chlorpyriphos or fenthion were studied as replacements for deltamethrin, in spite of the fact that most ticks are resistant to ethion. The authors propose a rotation strategy based on the alternation of several compounds together with a minimal frequency of dipping.