Herd-level seroprevalence and risk-mapping of bovine hypodermosis in Belgian cattle herds.

Our objective was to determine the seroprevalence of Hypoderma spp. and to develop a spatial model describing the risk surface of warble-fly infection in Belgian cattle herds (adjusting for herd size, herd type, local temperature, rainfall, relative air humidity and land-cover). This survey was carried out in 390 selected herds of all types (dairy, mixed and beef) from December 1997 to March 1998, which were included in a national infectious bovine rhinotracheitis and paratuberculosis (Johne's-disease) survey. All animals >24 months old were blood sampled and an ELISA was used on pooled serum samples (10 animals per pool). The herd seroprevalence was 48.7% (95% confidence interval: 43.6-53.8); positive herds were mainly in the south of the country and along the North Sea coast. The logistic multiple-regression model of herd-level seropositivity indicated that mixed-type and beef-cattle herds have more than four-fold and two-fold increases in the odds of being Hypoderma-positive, respectively, compared with dairy herds.

Humoral immune response in calves to single-dose, trickle and challenge infections with Fasciola hepatica.

In cattle experimentally infected with Fasciola hepatica, parasite specific IgG1 and IgG2 responses were studied. Additionally parasite specific IgE production was assessed by the Passive Cutaneous Anaphylaxis reaction. The primary infection was administered either as a single-dose or as a trickle infection over a 4-week period. Animals were challenged 4 months later. Titres of IgG1 and IgG2 against excretory-secretory parasite products (FhESAg), and against a whole-worm extract (FhSomAg) were measured by enzyme-linked immunosorbent assay (ELISA) in relation to weight gain, serum hepatic enzyme levels, and fluke infection rate. At necropsy, the mean number of flukes recovered was similar in both infected groups. The two ELISAs specific for bovine IgG1 showed analogous sensitivity and specificity (92% and 94%). Cross-reactivity was observed towards Echinococcus granulosus, Cysticercus tenuicollis, and C. ovis but not towards C. bovis, Cooperia spp., and Ostertagia spp. FhESAg gave rise to apparently more stable specific IgG1 titres as compared to FhSomAg. Mean IgG1 titres were significantly higher in the single-dose-infected group than in the trickle-infected group during the early migratory phase of the infection (week 2 to week 4 (FhSomAg) or week 6 (FhESAg)). IgG2 values were consistently lower than IgG1 levels. The kinetic response of both isotypes yielded a similar pattern. Specific IgE antibodies were detected in cattle of both infected groups from week 2 post-primary infection (PPI) onwards. The mean serum glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (gammaGT) activities were significantly higher in the single-dose-infected group for 3 weeks around peak levels (12-14 weeks PPI and 14-16 weeks PPI for GLDH and gammaGT respectively). Western blotting revealed a major antigenic fraction in FhESAg (26-30 kDa) recognized specifically by sera from F. hepatica infected calves as early as 6-8 weeks PPI. Experimental challenge caused no statistically significant modification of any parameter (IgG1 and IgG2 titres, enzymatic activities, immunoblotting) used to monitor the course of the infection. No correlation was found between fluke size and number, and antibody titres, suggesting that IgG1 production has little protective effect against F. hepatica infection.

Serological and biochemical follow-up in cattle naturally infected with Fasciola hepatica, and comparison with a climate model for predicting risks of fasciolosis.

Several biological parameters were measured in 31 heifers naturally infected with Fasciola hepatica during one grazing season in the Belgian Ardennes. A forecast model based on daily temperature used to assess the risk of fasciolosis was fitted to this assay. Cattle were turned out to two pastures. Each pasture was divided into two plots: one was treated with calcium cyanamide and the other was left untreated. The Lymnaea truncatula snails were counted on three different occasions. The results indicated a poor molluscicide efficiency. Body weight gains, anti-Fasciola antibody levels, faecal egg counts, levels of sorbitol dehydrogenase (SDH) and gamma-glutamyl transferase (gamma GT), packed cell volumes, white blood cells and differential leucocyte counts were determined monthly. No statistically significant difference was observed between animals from the two plots regardless of the recorded data. No correlation was found between body weight gains and other biological data. The sampling date had a significant effect on the antibody responses within a same group, and on the enzymatic levels for all groups combined. The forecast results were consistent with the recorded data. Temperature was a major bioclimatic constraint on the transmission of life cycle, and risk of infection occurred mainly in late spring (May/June) and in early September. Current results might be used to issue advice on the need for flukicide treatment of cattle. The indicators of the infection considered alone were useless and it is concluded that herd diagnosis of fasciolosis may rely on the rise of specific antibody levels, possibly associated with an increase in hepatic enzyme activities.

[Bovine hypodermosis in north-eastern Algeria: prevalence and intensity of infestation]. / Hypodermose bovine dans le Nord-Est algérien: prévalence et intensité d'infestation.

Between 1989 and 1997 different factors related to warble fly infestation (prevalence, intensity, climate, breed) were studied in north-eastern Algeria. Mean prevalence during the period was 76%. This figure was obtained from a cattle market survey of four different regions (Jijel, Constantine, Guelma, and El Tarf). One-hundred percent of the herds were found to be infested in El Tarf and 61% of animals were infested. Within a herd, the intensity of infestation decreased with the age of the cattle. The mean number of warbles per animal decreased as reinfestations occurred. The peak of the emergence of warbles observed between January and March was progressively delayed in the older animals. Two species of Hypoderma were present in cattle in Algeria (H. bovis and H. lineatum) with a predominance of H. lineatum (63%) in the semi-arid area (Batna) and a majority of H. bovis (75%) in humid area (Jijel). Warbles appeared earlier in Batna (October) than in Jijel (November). The Prim'Holstein breed was more susceptible to the warble fly infestation than Montbeliard or local breeds. The implementation of a control programme for hypodermosis in Algeria is urgent. Control can be achieved through a mass treatment of cattle. This approach must take into account the factors described in this study which influence the epidemiology of the disease.

The pathology of Psoroptes ovis infestation in cattle with a special emphasis on breed difference.

In cattle, infestations with P. ovis are responsible for a severe dermatitis. The disease is very common in some breeds of beef cattle whereas dairy cattle such as Frisian Holstein are considered as resistant. In order to investigate the factors responsible for this marked breed susceptibility, the immune response to P. ovis under experimental and field conditions has been studied using serology, lymphocyte transformation assay, intradermal tests and passive cutaneous anaphylaxis in susceptible Belgian White and Blue (BWB) and resistant Frisian Holstein (FH) cattle. The results of published studies are reviewed in this paper; original data on specific hypersensitivity reactions to P. ovisare also presented. The use of a sandwich ELISA allowed the detection of specific antibodies as early as 7 days post-infestation and very high titres were observed. There was a clear positive correlation between the antibody titre and the extent of lesions. This antibody response was associated with a marked in vitro lymphocyte proliferation but there was no difference between susceptible and resistant cattle. The passive cutaneous anaphylaxis test revealed the presence of specific Ig E in actively infested animals irrespective of the breed. Specific Ig E were detected fairly late during the course of an experimental infestation with P. ovis. The intradermal injection of P. cuniculi antigenic extract induced an immediate reaction in all animals including the controls; in contrast, a delayed hypersensitivity reaction was observed in infected BWB animals only. It is concluded that immunological as well as non-immunological factors may be responsible for the breed related susceptibility or resistance to P. ovis.

The relationship between parasite counts, lesions, antibody titres and daily weight gains in Psoroptes ovis infested cattle.

Psoroptes ovis counts, extent of lesions (clinical index: ClinI), daily weight gains (DWGs) and anti-P. cuniculi antibody titres in ELISA were recorded during seven therapeutic field trials. Relationship between these different data were studied. The differences between the mean DWG of treated and untreated control animals of the different trials ranged from 39 to 1206 g/day. Data were pooled for statistical analysis and the influence of trial conditions (management of the herd, farm, treatment) was extracted from each individual data by subtracting, from the DWG of each animal, the mean DWG of its trial. Such data were called daily weight gain over the trial mean (DWG/TM). Multiple regression of DWG/TM, calculated over the period between the clinical examinations in control animals (n = 40), on clinical indices and sex demonstrated a significant DWG/TM reduction per percentage of affected body surface according to the following equation: DWG/TM (in g/day)= 135-22 ClinI(0)-13 ClinI(28/35)-70 (if male) (R2 adjusted = 0.39), where ClinI(0) and ClinI(28/35) are the clinical indices recorded respectively at the beginning (day 0) and at the end (day 28 or 35) of the experimental period during which the animals were left untreated. A nonsignificant relationship (R2 adjusted = 0.07) was found between the antibody titres on day 28 or 35 and the individual DWG/TM This would suggest that serology could be used to estimate the prevalence of the disease on a local or national basis but not to calculate its economic impact.

Humoral and cell-mediated immune responses of beef and dairy cattle experimentally infested with Psoroptes ovis.

OBJECTIVE: To compare cellular and humoral immune responses of beef (Belgian White and Blue [BWB]) and dairy (Friesian-Holstein [FH]) cattle to Psoroptes ovis infestation and to determine whether P ovis infestation impaired immune responses to infectious bovine rhinotracheitis virus (IBR) vaccine or an immunogenic protein (keyhole-limpet hemocyanin [KLH]). ANIMALS: 19 BWB and 6 FH 1-year-old calves. PROCEDURE: 2 trials were performed. In each trial, 7 (trial 1) or 6 (trial 2) BWB calves and 3 FH calves were experimentally infested with P ovis and 3 BWB calves were maintained as uninfested controls. Animals were inoculated with KLH and IBR virus vaccine twice; 3 BWB calves in each trial were treated with ivermectin. Serum antibody responses to KLH, IBR virus, and P ovis were measured by use of ELISA. A lymphocyte transformation assay was used to determine nonspecific responses to 3 mitogens and specific lymphocyte reactivity to P ovis antigen. RESULTS: In each trial, 3 BWB and 3 FH calves developed clinical signs of psoroptic mange and mites could be recovered. Infested and control animals developed similar antibody titers to KLH and IBR virus. Antibodies to P ovis were detected early in some infested calves, and this was correlated with a marked cell-mediated immune response. Lymphocyte responsiveness to the 3 mitogens was not significantly different among groups. CONCLUSIONS: In these calves, infestation with P ovis induced a marked humoral and cell-mediated immune response. Immunosuppression was not evident.

Comparative efficacy of different insecticides in the treatment of cattle hypodermosis in north-eastern Algeria.

The efficacy of different drugs (microdose of ivermectin, doramectin and moxidectin at the recommended doses and topically applied rotenone) against the first, second and third instar larvae of Hypoderma bovis and H. lineatum was studied in cattle in the El Tarf area (northeastern Algeria). Before performing the efficacy trials, the life cycle of the warble fly was studied at the slaughterhouse between July 1993 and June 1994. This survey revealed that both species of warble fly were present in this area: L1 larvae of H. lineatum were found around the oesophagus between August and January, whereas L1 larvae of H. bovis were observed around the spine from November until March. Warbles were present under the skin from the end of October until May. The nymphal phase took place between February and May. As a result of this study the authors recommend applying chemoprophylaxis (treatment against L1) in September. This work also confirmed the excellent efficacy of avermectins and milbemycins against the three instar larvae of Hypoderma sp. under the field conditions prevailing in Algeria. Rotenone has a lower efficacy (95%) which is limited to the second and third instar larvae. However, this drug appears useful in dairy cattle.

Field efficacy of injectable doramectin against Chorioptes bovis in naturally infected cattle.

A single subcutaneous injection of doramectin at a dose rate of 200 micrograms/kg bodyweight was effective in controlling an infection of Chorioptes bovis mites in naturally infected cattle. From 14 days after treatment, the geometric mean number of live mites was significantly lower (P < 0.001) in the doramectin-treated cattle than in the control group at each sampling until day 35. The percentage efficacy (treated versus controls) of doramectin against C bovis at day 35 was 99.9 per cent and the percentage reduction (day 35 versus day 0) in the treated animals was 99.3 per cent. At day 35, all seven controls were still positive for C bovis whereas five of the eight doramectin-treated animals were free of live mites.

Antibody response after treatment in cattle infected with Psoroptes ovis.

The decline of anti-Psoroptes ovis antibody titres after treatment was studied in six groups of naturally infected cattle. In all trials, using a limiting dilution technique, the specific antibody levels were assessed by ELISA on sera collected at regular intervals up to 78 days post treatment. All individual antibody titres started to decline between day 7 and day 14 post treatment. A linear decrease was observed. In a limited trial, five experimentally infected animals were bled monthly after treatment and seronegativity was reached within four months. The results obtained were in agreement with those obtained in the five field trials. Using a linear regression model, it was estimated by interpolation that most of the animals would have been seronegative within seven months post treatment. These results suggest that the exposure to specific P ovis antigen stops with the end of parasite activity and that dead mites are relatively non-immunogenic.

Efficacy of pour-on and injectable formulations of moxidectin and ivermectin in cattle naturally infected with Psoroptes ovis: parasitological, clinical and serological data.

On the basis of Psoroptes ovis counts performed on day -7, 32 animals were randomly allocated to a control group of five animals or to four groups comprising six or seven animals which were treated, respectively, with pour-on ivermectin (IPO), injectable ivermectin (II), pour-on moxidectin (MPO) and injectable moxidectin (IM). Living mites were counted in skin scrapings on days 0, 7, 14, 28, 42 and 56 post-treatment (PT). Lesions were recorded on a standardized map on days 0 and 56 PT. Antibody kinetics were studied using ELISA on serially diluted sera. The antibody titres were expressed as the dilution giving the positive/negative cut-off. Until their treatment on day 28, the control animals remained parasitologically positive and their antibody titres increased. In treated groups, all living mite counts were negative on days 28 and 42 PT but some animals were still infected on days 7 and 14 PT. On day 56, living P. ovis were found in one animal of the IPO group. An equation of regression describing the antibody decrease was calculated with each individual data set. In most of the treated animals, the coefficient of determination R2, which describes the closeness of fit to the linear model, was above 0.9. The linear model could not be applied (low R2) to the antibody kinetics of four animals: the day 56 positive animal and its two neighbours in the IPO group and one animal from the MPO group. In the treated groups, the differences between the numbers of infected animals, the mean daily weight gains or the mean antibody titres were not statistically significant. Mean daily weight gains of the treated groups were higher than in control animals.

Sero-surveillance of hypodermosis in a herd under therapeutic control. Effect of a low level of infestation.

A cattle herd from the experimental farm of INRA in Nouzilly has been treated for hypodermosis since October 1990. Additionally, a regional eradication scheme has been implemented in this area since autumn 1992. Bi-monthly warble counts were performed between March and July each year on an average of 200 animals. No warble was recorded in this herd from 1991 to 1994 with the exception of two dairy cows in 1993. In autumn 1994, therapeutic control measures were stopped. Serological surveys were performed in the autumn of each year from 1991 until 1995. Anti-Hypoderma antibodies were found in 25%, 27.2%, 4.3%, 3.2% and 0% of the animals respectively. An experimental low infestation was conducted in the summer of 1994. During the spring 1994, third instars of Hypoderma bovis were collected from naturally infested animals. From a total of 13 pupae, six adults (four males and two females) emerged and were released in the herd of Nouzilly on 24 June and 4 July. In October 1994 serological investigations revealed two animals seropositive for hypodermosis. This number increased to six in January 1995. The antibody kinetics of these six animals remained parallel throughout the next 6 months: the titres increased up to April and started to fall in May to return to negative values in August. Manual examinations of the animals at weekly intervals between April and July revealed the presence of four warbled animals with one, one, two and three warbles respectively. The two other seropositive animals remained warble free. One other animal showed antibody titre fluctuations between negative and low positive values, but was warble free in the spring. In October 1995 all the animals of the herd were seronegative. The interpretation and the value of a sensitive immunodiagnosis in a large eradication programme are discussed and compared with warble counts, especially in the case of a low level of infestation.

A sandwich enzyme-linked immunosorbent assay to study the antibody response against Psoroptes ovis in cattle.

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed using polyclonal antibodies from Psoroptes cuniculi infested rabbit and a crude P. cuniculi antigen. Sera from 133 Psoroptes ovis infested and 137 uninfested cattle were serially diluted from 1:100 to 1:102,400 and analyzed. Curves obtained by plotting log dilution versus optical densities (OD) were used and a working dilution of 1:400 was selected. Positive/negative cut-off values were calculated using the mean OD percentage (6%) of all negative sera plus 3 standard deviations. Sensitivity and specificity according to the resulting cut-off (25%) were 98.5% and 97.8% respectively. Expressed as the dilution giving the cut-off value, results in ELISA revealed a wide range of antibody titres (from 1:19 up to 1:2,240,000) with a geometric mean value of 1:35,480, and this is probably related to the well-described hyperglobulinemia in P. ovis infestations. In two trials performed at a 1 year interval, 19 Belgian White and Blue and six Fresian-Holstein calves were experimentally infested, and sensitivity and specificity were calculated throughout the experimental period. Sensitivity reached 78% on day 70 in trial 1 and 100% on day 49 in trial 2 (sensitivity was calculated using data from three control animals, three infected Fresian-Holstein animals and seven (trial 1) or six (trial 2) infected Belgian White and Blue animals). Specificity on day 0 was 100% in trial 1 and 92% in trial 2. At the end of both trials, specificity decreased in 80%. The development of the serum antibody activity to Psoroptes antigens was correlated with the development of lesions: in trial 1, the coefficient of correlation between the percentage of body surface with lesions and antibody titre was 0.82 (probability of no relationship P < 0.005) on day 56 post-infection (PI) and in trial 2, 0.83 (P < 0.025) and 0.87 (P < 0.025) on days 35 and 63 PI respectively.

Field efficacy of moxidectin 0.5% pour-on against Chorioptes bovis, Damalinia bovis, Linognathus vituli and Psoroptes ovis in naturally infected cattle.

Field efficacy of a pour-on formulation of moxidectin, a macrocyclic lactone endectocide, was evaluated in cattle naturally infested with Chorioptes bovis, Damalinia bovis, Linognathus vituli and Psoroptes ovis. In trial 1, two experimental groups of cattle naturally infested with P. ovis were formed. Group 1 animals remained as untreated controls whereas Group 2 animals were treated on day 0 with 0.5% moxidectin cattle pour-on at a dose of 0.5 mg kg-1 bw. Efficacy was assessed by (a) taking skin samples from each animal on days -4, 7, 14, 21, 28, 42 and 56 post treatment (PT) and observing the numbers of viable P. ovis mites and (b) clinical examination of animals on days 7, 14, 21, 28, 42 and 56 with the percentage of affected body surface calculated and live body weights recorded for each animal on days 4, 28 and 42. The pour-on formulation of moxidectin yielded excellent efficacy as no live mites were found in treated animals at 14, 21, 28, 42 and 56 days PT, except in one animal from which one adult mite was collected on day 42. Clinical indices showed a regular decrease in the affected body surface area. All untreated animals but one remained positive until day 28 and their clinical condition worsened rapidly. In trial 2, two experimental groups of cattle naturally infested with D. bovis and L. vituli were selected. Group 1 remained as untreated controls whereas Group 2 individuals were treated on day 0 with 0.5% moxidectin cattle pour-on at a dose of 0.5 mg kg-1 bw. Efficacy was assessed by identifying and counting lice on eight 15 cm hair partings at predefined anatomical sites on days 0, 14, 28 and 42. On the basis of animals cured and lice count reduction, efficacies were 100% on day 14 and from then onwards for both species. In trial 3, 24 animals naturally infested with C. bovis were divided into three experimental groups comprising eight (Group I), seven (Group 2) and nine animals (Group 3). Group 1 was the untreated control group whereas Groups 2 and 3 animals were treated on day 0 with 0.5% moxidectin cattle pour-on at a dose of 0.25 mg and 0.5 mg kg-1 bw, respectively. Efficacy was assessed as in trial 1. Skin scrapings were collected on days -3, 7, 14, 28, 42 and 56 PT. A clinical index was calculated for each animal on days 0, 28 and 56 whereas body weights were recorded on days 0 and 56. At 0.25 mg kg-1 bw, the efficacy of moxidectin cattle pour-on against C. bovis was incomplete. In contrast, at a dose of 0.5 mg kg-1 bw, moxidectin cattle pour-on was fully effective and by day 14 PT all animals were negative for C. bovis and remained so until the end of the trial. No side effects were observed during these three trials. These results indicate that at a dose of 0.5 mg kg-1 bw, the pour-on formulation of moxidectin is highly effective against C. bovis, D. bovis, L. vituli and P. ovis.

The efficacy of moxidectin 0.5% pour-on against Hypoderma bovis in naturally infested cattle: parasitological and serological data.

The field efficacy of moxidectin 0.5% pour-on formulation was assessed in heifers naturally infested with Hypoderma bovis. After their first grazing season in an infested area 34 heifers were selected on the basis of results of an ELISA test performed in January 1992. Twenty-five animals were treated with moxidectin 0.5% pour-on at a dose of 0.5 mg kg-1 bodyweight and nine heifers were left untreated. No local or general side-effects associated with the treatment were noticed. In April, seven of the nine untreated heifers were affected by warble fly, and in May all were infested; none of the treated animals harboured warble fly at any time during the trial. All the extracted larvae were identified as Hypoderma bovis. On the basis of the warble counts, efficacy was 100%. The antibody kinetics, studied on blood samples collected on Days 0 (14 January), 6, 27, 48, 90, 119 and 150, showed that in the untreated animals, the antibody titres increased until May (Day 119) and then declined sharply, whereas in the treated animals there was a drop from Day 30 onwards. The mean ELISA titres of the control and treated groups became significantly different from Day 48 onwards (P < 0.05). In conclusion, moxidectin 0.5% pour-on formulation at a dose of 0.5 mg kg-1 bodyweight can effectively treat cattle naturally infested with Hypoderma bovis first instar larvae.

Field efficacy of injectable moxidectin in cattle naturally infested with Chorioptes bovis and Sarcoptes scabiei.

Field efficacy of moxidectin, a macrocyclic lactone endectocide, was evaluated in cattle naturally infested with Chorioptes bovis and Sarcoptes scabiei. Eight animals were allocated to two groups of four animals each, based on parasitological and clinical status. Animals of the treated group received one subcutaneous injection of injectable moxidectin at 0.2 mg kg-1 body weight on Day 0. Individuals of the control group received emergency treatment of a single injection of moxidectin at 0.2 mg kg-1 body weight on Day 28. Efficacy was assessed by (a) taking skin samples from each animal on Days 0, 7, 14, 21, 28, 42 and 56 and observing the numbers of viable mite stages and species and (b) clinical examination of animals on Days 7, 14, 21, 28, 42 and 56 with the percentage of affected body surface calculated for each animal on Days 0, 28 and 56. On the basis of the geometric means from treated and control animals, the percentage reductions in the total numbers of living C. bovis mites on Days 7, 14, 21 and 28 were 69, 87, more than 99 and 98, respectively. However, at the end of the trial, only two animals were negative for C. bovis. The percentage reductions in the total numbers of S. scabiei on Days 7, 14, 21 and 28 were 93, 100, 100 and 100, respectively. Clinical indices of the treated animals showed a sharp decrease in the affected body surface area from a mean of 43.6% on Day 0 to 0.9% and 0% on Days 28 and 56, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Field efficacy of injectable and pour-on moxidectin in cattle naturally infested with Psoroptes ovis (Acarina: Psoroptidae).

Field efficacy of moxidectin, a macrocyclic lactone endectocide, was evaluated in cattle naturally infested with Psoroptes ovis. Three groups of six animals were used based on parasitological and clinical status. Group 1 animals received one subcutaneous injection of injectable moxidectin at 0.2 mg kg-1 body weight; Group 2 animals received topically one dose of 0.5 mg kg-1 body weight of pour-on moxidectin; Group 3 individuals remained untreated as controls. Efficacy was assessed by (a) taking skin samples from each animal on Days -4, 14, 28, 42 and 56 post-treatment (PT) and observing numbers of viable mite stages and species and (b) clinical examination of animals on Days 14, 28, 42 and 56 with the percentage of affected body surface calculated for each animal on Days -4, 28 and 56. Both formulations gave 100% efficacy as no live mites were found in Groups 1 or 2, 14, 28 and 56 days after treatment. Clinical indices showed a sharp decrease in the affected body surface area from a mean of 5.48% and 6.1% on Day -4 in Groups 1 and 2, respectively, to 0% in both groups on Days 28 and 56 PT. All untreated animals remained positive until Day 28. The clinical condition of the controls worsened rapidly during the experiment (mean clinical index: 2.87% and 13.05% on Days -4 and 28, respectively) and they were given an emergency treatment on Day 28. No side-effects were observed with either formulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Field efficacy of flumethrin pour-on against Psoroptes ovis in cattle.

The field efficacy of pour-on formulation of flumethrin 1 per cent was assessed in cattle naturally infested with Psoroptes ovis. In a finishing unit, 18 infested animals were selected, left untreated for one month and examined twice to monitor the progress of the infestation. They were treated twice 10 days apart with a pour-on formulation of flumethrin 1 per cent (2 mg/kg bodyweight). Skin samples were collected from the animals on days 0, 7, 14, 28 and 42 and examined for the presence of live mites. The clinical condition of the cattle was evaluated at the beginning and at the end of the trial using a standardised chart. Bodyweights were recorded on days -32, 0, 28 and 50. In addition the 65 cows in a calving unit were given the same treatment regimen and its efficacy was evaluated on days 0, 7, 14 and 28 in 11 P ovis infested animals. On the day of treatment most of the infested animals had a severe pyodermatitis. From day 7 onwards no live mites were found in the treated animals and there was a marked clinical improvement. The percentage efficacy on day 28 was 100 per cent in both units. In the finishing animals treatment was associated with a marked improvement in daily weight gains between day 0 and day 28.