Relationship between lice infestation and leather damage in cattle

Systematic review of hematophagous arthropods present in cattle in France

The arrival of pathogens, whether zoonotic or not, can have a lasting effect on commercial livestock farms, with dramatic health, social and economic consequences. However, available data concerning the arthropod vectors present and circulating on livestock farms in France are still very imprecise, fragmentary, and scattered. In this context, we conducted a systematic review of the hematophagous arthropod species recorded on different types of cattle farms in mainland France (including Corsica). The used vector "groups" studied were biting flies, biting midges, black flies, fleas, horse flies, lice, louse flies, mosquitoes, sand flies, and ticks. A large number of documents were selected (N = 9,225), read (N = 1,047) and analyzed (N = 290), allowing us to provide distribution and abundance maps of different species of medical and veterinary interest according to literature data. Despite the large number of documents collected and analyzed, there are few data provided on cattle farm characteristics. Moreover, data on all arthropod groups lack numerical detail and are based on limited data in time and/or space. Therefore, they are not generalizable nor comparable. There is still little information on many vectors (and their pathogens) and still many unknowns for most studied groups. It appears necessary to provide new, updated and standardized data, collected in different geographical and climatological areas. Finally, this work highlights the lack of entomologists, funding, training and government support, leading to an increased risk of uncontrolled disease emergence in cattle herds.

Effectiveness of a fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) against Rhipicephalus microplus and sucking lice infesting cattle

Unmanaged tick and sucking lice infestations negatively impact the health and production potential of cattle. Described herein are two non-interference dose confirmation studies evaluating the efficacy of a single administration of a new fixed-dose combination injectable (FDCI) endectocide consisting of 0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride, against either laboratory-induced Rhipicephalus microplus infestations in Australia or naturally acquired sucking lice (Linognathus vituli) infestations in the US. This FDCI is available as Dectomax V® in Australia and New Zealand and as Valcor® in the United States. To evaluate therapeutic efficacy against R. microplus, 12 calves were each exposed to 10 infestations of ∼5000 larvae per infestation between Days -24 and -2. Calves were either treated on Day 0 with the FDCI or left untreated (control). Additional R. microplus infestations of ∼5000 larvae were conducted on Day 2 and then three times weekly to also evaluate persistent efficacy of the FDCI. Tick collections were conducted daily from Day -3. Group mean live tick counts, egg production, and egg viability were analyzed for significant differences between the two groups. To determine efficacy of the FDCI against lice, 24 cattle with active sucking lice infestations based on Day -7 counts were allocated to two groups and treated on Day 0 with either saline (control) or the FDCI. Lice counts were conducted weekly from Day 14 through 42 and again on Day 56. Mean group lice counts on each count day were compared between treatment groups. In the R. microplus study presented here, cattle in Queensland, Australia treated with the FDCI (Dectomax V®) showed > 90 % reduction in tick counts based on arithmetic means within 48 h of treatment when compared to untreated cattle, and counts were > 95 % reduced from post-treatment Day 5 through Day 30. In the sucking lice study conducted in the US, the FDCI (Valcor®) displayed 100 % efficacy against sucking lice infestations (L. vituli) from first count day (Day 14 post-treatment) through Day 35 and then 99.9 % efficacy through Day 56 post-treatment. No treatment-related adverse events were reported for cattle in either study. Using R. microplus and sucking lice as representative ectoparasites, these studies demonstrate the ectoparasite activity of doramectin is retained in the new FDCI.

A pilot study on the prevalence of lice in Irish beef cattle and the first Irish report of deltamethrin tolerance in Bovicola bovis

Background

Pediculosis in cattle causes significant itching, irritation and stress to the animal, often resulting in skin damage and poor coat condition. The control of bovine pediculosis in Ireland is based predominantly on commercial insecticides belonging to one of two chemical classes, the synthetic pyrethroids and the macrocyclic lactones. In recent years, pyrethroid tolerance has been reported in a number of species of livestock lice in the United Kingdom and Australia.

Results

In this pilot survey, lice were detected in 16 (94%) out of 17 herds visited. Two species of lice, Bovicola bovis and Linognathus vituli were identified. In vitro contact bioassays showed evidence of deltamethrin tolerance in Bovicola bovis collected from 4 farms. This was confirmed by repeatedly assessing louse infestations on treated animals on one farm.

Conclusions

To our knowledge this is the first record of insecticide tolerant populations of lice in Irish cattle. The results also provide new data on the species of lice infesting beef cattle in Ireland and the prevalence and control of louse infestations in Irish beef cattle herds.

Prevalence and distribution of lice on sheep and cattle farms in Great Britain

Lice are common production-limiting ectoparasites affecting livestock. Up-to-date data on their prevalence and spatial distribution on farms in Great Britain is important given that prevalence is believed to be increasing as a result of insecticide resistance. Here the prevalence of farms reporting lice, and factors associated with louse presence, were assessed using a retrospective questionnaire. For sheep and cattle farms, 16.1 % and 15.8 % reported lice on their livestock, respectively. Beef farms were more likely to report lice than dairy farms, with a prevalence of 18.0 % and 7.8 %, respectively. For sheep farms, prevalence was highest in Wales (27.7 %) and Scotland (22.4 %). For cattle farms, prevalence was highest in Scotland (27.6 %), Wales (18.5 %) and SW England (18.5 %). For sheep farms, statistical hotspot clusters were identified in Wales, NW England and SW Scotland, with prevalence in these areas ranging from 30.7 to 40.0%. For cattle farms clustering of cases was less evident. Multivariable analysis showed that significant factors associated with lice on sheep farms were larger flock sizes and geographic location (Scotland or Wales). For beef cattle farms, significant associated factors were larger herd sizes and upland grazing. More than 90 % of farms that reported lice, also reported treating for lice.

Preliminary investigations into the effect of ostrich feather lice (Struthiolipeurus struthionis) on production and leather quality

The effect of ostrich feather lice (Struthiolipeurus struthionis) on productivity and leather quality was investigated in the light of louse-related skin damage on other livestock species that seems similar to defects, called pitting, seen on ostrich skins. The occurrence and spread of feather lice on ostriches were also studied. Natural infestation of louse-free ostriches within a group mixed with louse-infested ostriches was achieved within 6 months. Lousiness was determined by visual counts on the body and feathers of the ostriches on five locations. There was a relatively low correlation between the number of lice observed on the live ostriches and the actual number of lice extracted from harvested wing feathers. However, it was demonstrated that lice obtained from feathers increased at a rate of 3.29 (s.e. = 1.34) lice per 100 g of feathers for an increase of one louse observed on the live birds in the paddock (R2 = 0.23). Treatment with synthetic pyrethroid insecticides eradicated all lice. Louse infestation had no significant influence on growth or slaughter traits, while no causal relationship between louse infestation and pitting damage on the processed ostrich skins could be demonstrated.

An Immunohistochemical Assessment of the Cutaneous Immune Response to Louse Infestation in Cattle

Skin samples were taken from 10 experimental cattle exposed naturally, during a period extending over two winters, to Bovicola bovis and Solenoptes capillatus, five becoming infested and five being protected from infestation by repeated treatment with ectoparasiticides. Skin sections were examined histopathologically and immunohistochemically for expression of the immune cell markers CD3, CD4, CD8 and class II antigens of the major histocompatibility complex (MHC). Louse-infested cattle had a mixed infiltration of the superficial dermis and perifollicular regions with eosinophils and mononuclear cells. The skin of infested cattle differed from that of non-infested cattle in showing significantly more cells expressing CD3, CD4 and MHC class II (P<0.05). Many of the MHC class II(+) cells had dendritic morphology, suggesting active antigen presentation within the lesions. Louse infestations have previously been thought to produce a type 1 hypersensitivity response, mediated by Th2 lymphocytes. However, the increased number of lymphocytes and antigen-presenting cells observed in the present study suggests that in chronic infestation there is activation of local cell-mediated (Th1) immunity.

Control of the cattle louse Bovicola bovis with the fungal pathogen Metarhizium anisopliae

The effects of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) were evaluated against the common louse parasite of cattle, Bovicola bovis (Piaget) (Trichodectidae: Ischnocera). Two different concentrations and formulations of conidial suspensions were applied to contained populations of adult female lice. In vitro, lice immersed in suspensions of M. anisopliae formulated in 0.03% Tween 80 developed infections; at the highest concentration (1x10(8)conidia ml-1) a mean of 71% (+/-11.52%, 95% C.I.) of lice became infected. Lice exposed to the Tween 80 only in vitro, showed high levels of survival and zero infection. In vivo, fungal conidia were applied to louse populations contained in 7 cm diameter circular arenas glued to the backs of Holstein cattle, maintained in controlled climate conditions. Conidia were formulated in either Tween 80 or silicone oil. The treatment with M. anisopliae resulted in high levels of infection and there was no overall difference between the two formulations in the number of infections observed. At the highest concentration (1x10(8)conidia ml-1) a mean of 73% (+/-15.57%, 95% C.I.) lice became infected. It is concluded that the strategic seasonal use of a fungal pathogen on cattle, applied in early winter, may be of value in suppressing the winter increase in abundance, preventing the population increasing to clinically significant levels.

Therapeutic and persistent efficacy of spinosad applied as a pour-on or a topical spray against natural infestations of chewing and sucking lice on cattle

Studies were conducted in Wisconsin and Illinois, USA, to assess and compare the therapeutic and persistent efficacy of spinosad when applied as either a pour-on or topical spray and compared with cyfluthrin pour-on and coumaphos topical spray for controlling natural infestations of chewing (Bovicola bovis) and sucking (Linognathus vituli, Solenopotes capillatus and Haematopinus eurysternus) lice on cattle. Thirty-five animals at each trial site were blocked according to pre-treatment lice counts and randomly allocated to one of five treatment groups: single treatments of spinosad (25 g/L), diluted with water to 0.04% active ingredient and applied as a whole-body topical spray; spinosad (25 g/L) applied as a neat pour-on at 2 mg/kg body weight; Co-Ral Emulsifiable Livestock Insecticide (5.8% coumaphos), diluted to 0.03% active ingredient and applied as a whole-body topical spray; CyLence Pour-on Insecticide (1% cyfluthrin), applied as a neat pour-on at the manufacturer's recommended use rate for lice; and untreated control. Both spinosad treatments and cyfluthrin provided > or =96% control of B. bovis for up to 7 weeks, whereas the efficacy of coumaphos dropped to <90% after week 5 at one site. Spinosad spray had the best therapeutic and residual control of all treatments against L. vituli, > or =98% for at least 5 weeks at both sites, compared with 3 weeks for coumaphos at one site. Spinosad and coumaphos sprays provided 100% control of S. capillatus for at least 8 weeks compared with > or =97% control for spinosad and cyfluthrin pour-on treatments over the same interval. While H. eurysternus burden was low and limited to one study site, all four treatments provided 100% control for at least 6 weeks. These studies showed that topically applied spinosad provided a high degree of therapeutic and residual control against both sucking and chewing lice.

Prevalence of anthelmintic resistant cyathostomes on horse farms

OBJECTIVE

To determine prevalence of anthelmintic resistance in cyathostome nematodes of horses in the southern United States.

DESIGN

Cross-sectional study.

ANIMALS

786 horses on 44 farms and stables in Georgia, South Carolina, Florida, Kentucky, and Louisiana.

PROCEDURE

Fecal egg count (FEC) reduction tests were performed on 44 large farms and stables. Horses on each farm were treated with an oral paste formulation of fenbendazole, oxibendazole, pyrantel pamoate, or ivermectin at recommended label dosages. A mixed linear model was fitted to the percentage reduction in FEC, accounting for differences among farms, states, ages, treatments, and treatment by state interactions.

RESULTS

By use of a conservative measure of resistance (< 80% reduction), the percentage of farms with anthelmintic-resistant cyathostomes was 97.7%, 0%, 53.5%, and 40.5% for fenbendazole, ivermectin, oxibendazole, and pyrantel pamoate, respectively. Mean percentage reductions in FEC for all farms were 24.8%, 99.9%, 73.8%, and 78.6% for fenbendazole, ivermectin, oxibendazole, and pyrantel pamoate, respectively. Pairwise contrasts between states for each treatment revealed that in almost all instances, there were no significant differences in results between states.

CONCLUSIONS AND CLINICAL RELEVANCE

The prevalence of resistance found in this study was higher than that reported previously, suggesting that anthelmintic resistance in equine cyathostomes is becoming a major problem. Furthermore, data from these 5 southern states, which are geographically and physiographically distinct, were remarkably similar. This suggests that drug resistance in cyathostomes is highly prevalent throughout the entire southern United States and probably nationwide.