Bovicola Caprae Research Articles

First Insight into the Phylogenetic Diversity of Bovicola caprae Infesting Goats of Different Agro-climatic Locations in India.

Bovicola caprae is an important obligate ectoparasite of goats worldwide including India. The present study aimed at the molecular confirmation, phylogenetics and population structure analyses of B. caprae infesting goats of three different agro-climatic locations in India, by targeting the mitochondrial cytochrome C oxidase subunit 1 (cox1) genetic marker. The phylogenetic tree exhibited the presence of two different lineages of B. caprae. The sequences generated herein clustered in lineage 2 along with theGenBank™ archived sequences from China and Iran. The sequences generated herein also showed the circulation of sub-lineages of B. caprae in India based on the analysis of pairwise genetic distances between sequences and median-joining haplotype network. The population structure analyses revealed low nucleotide (0.00353 ± 0.00291 and 0.02694 ± 0.00363) and high haplotype (0.667 ± 0.314 and 0.618 ± 0.104) diversities for the present study isolates as well as for the complete dataset, respectively, which evinced a recent demographic expansion. High genetic differentiation (FST value = 0.97826) and low gene flow (Nm = 0.00556) were also recorded in the different lineages/populations. In conclusion, the present study addressed the research gap and provided the first insight into the phylogenetics of the goat louse B. caprae and highlighted the circulation of sub-lineages of the ectoparasite in India.

Molecular detection of hemotropic Mycoplasma and Bartonella species in lice from sheep and goats of Mexico.

The knowledge of lice associated with small ruminants, especially sheep and goats, is scarce. In Mexico, there are historical reports of six species of chewing and sucking lice associated with Capra hircus and Ovis canadensis. However, the reports did not analyze the ecology of the infestations or the presence of potentially pathogenic bacteria. For this reason, the objectives of this study were i) to identify the species of lice associated with sheep and goats in three states of the Mexican Republic, ii) to characterize the infestations, and iii) to identify the presence of bacterial pathogens. From October 2019 to August 2021, six ranches with sheep and goats were sampled in the states of Hidalgo and Veracruz. Hosts were visually inspected, and lice were retrieved with forceps. The specimens were sexed and identified using morphological taxonomic keys. DNA extraction was performed individually, and a fragment of the cytochrome oxidase subunit 1 gene (COI) was amplified for the molecular identification of the specimens. Subsequently, Anaplasma, Bartonella, Ehrlichia, Mycoplasma, and Rickettsia were molecularly detected. Additionally, the infestations were characterized by calculating the prevalence and mean abundances. We collected 563 specimens of three species, Bovicola caprae, Bovicola ovis, and Linognathus africanus. The highest infestation levels were recorded for B. ovis (66.7%; 4.4) from Veracruz. Additionally, two Bartonella species were detected: Bartonella mellophagi in B. ovis and Bartonella capreoli in L. africanus. In contrast, Mycoplasma ovis was detected exclusively in one pool of B. ovis. This study provides new bacterial-ectoparasite associations and highlights the possible role of these neglected ectoparasites as vectors in the populations of sheep and goats from Mexico.

Identification of ectoparasitic insects among domestic goats in Bulgaria.

Ectoparasitic entomoses cause serious economic losses to small-scale farmers. Parasites have both direct and indirect impacts on hosts. Domestic goats are a common target of infestation with ectoparasitic insects. This study aimed to identify the species of ectoparasitic insects in domestic goats in Bulgaria. The study was performed in 34 farms from 29 settlements in 16 regions of Bulgaria. A total of 4599 goats from eight breeds, naturally infested with ectoparasitic insects were included in the study. The goats were inspected with a magnifying glass for the presence of skin changes (alopecia, dandruff, crusts, and nodules), eggs and adult ectoparasites. The detected insects were collected individually with tweezers and preserved in containers with 70% ethanol. Over the study period, 5,651 insects were collected; their species, sex, and developmental stage were identified by their morphological features and biometric measurements. Six species from 5 genera were detected: Linognathus stenopsis Burmeister, 1838; Linognathus africanus Kellog and Paine, 1911; Bovicola caprae Gurlt, 1843; Pulex irritans Linnaeus, 1758; Hippobosca equina Linnaeus, 1758; and Lipoptena cervi Linnaeus, 1758. Linognathus stenopsis were the most prevalent, followed by B. caprae and P. irritans. In detected lice populations, female insects were more numerous; female: male ratios ranged from 2.2 to 7.2 and imagines prevailed over the nymphs. In fleas, male imagines were more numerous than females (1:0.8). The study demonstrated that the species L. stenopsis, L. africanus, B. caprae, and P. irritans were encountered in more than 40% of surveyed farms, situated in 68.75% of regions in Bulgaria. The most intense infestation was by species from the Linognathus genus (907 insects), whereas the highest extensity of infestation was registered for P. irritans (32.3%). This study detected P. irritans as the only flea species.

CLINICAL AND HEMATO-BIOCHEMICAL STUDIES ON GOATS NATURALLY INFESTED WITH SUCKING AND BITING LICE

The current study was performed to assess the most common clinical symptoms and hemato-biochemical alterations in goats naturally infested with sucking and biting lice. A total of 4599 goats were included in the clinical investigation. The changes in concentrations of some hematological and biochemical parameters were evaluated using 20 naturally infested animals divided into 2 equal groups – group 1 (infested with Bovicola caprae) and group 2 (infested with Linognathus stenopsis). Blood samples were collected before the treatment with Eprinomectin and on the 30th and 60th-day post-treatment (DPT). After sampling, the blood was examined for changes in the complete blood cell count including RBC, HGB, HCT, RBC indices (MCV, MCH, MCHC, RDW), WBC, leukocyte differential count as well as some biochemical parameters (Ca, P, Fe, total protein, albumin, bilirubin, ASAT, ALAT, AP). Clinical demonstrations in infested goats were not specific, represented with rubbing, scratching, broken hairs, alopecia, skin secretion, inflamed lesions (papules), crusts, and keratinization. The changes found in the hematological and biochemical parameters were normocytic hypochromic anemia (p˂0.001) and hypoferremia (p˂0.01) in the goats infested with sucking lice (L. stenopsis) and leukocytosis (p˂0.001), hyperproteinemia (p˂0.001) and hyperalbumineamia (p˂0.05) in the animals infested with biting lice (B. caprae). All changed parameters have returned to the reference ranges on the 30th and 60th DPT.

Detection of pyrethroids resistance alleles in goat biting louse Bovicola caprae (Phthiraptera: Trichodectidae) in west and northwest of Iran.

Pyrethroid insecticides target voltage-gated sodium channels (VGSCs) that are essential for electrical signaling in the nervous system of insects. Three-point mutations at the corresponding amino acid sequence positions M815I, T917I, and L920F located in domain II conferring the knockdown resistance (kdr) are the most important mutations in pyrethroid-resistant lice worldwide. In addition, six new mutations have been reported in the extracellular loops IIS1-2 (H813P) and IIS5 (I927F, L928A, R929V, L930M, L932M) in the α- subunit of the sodium channel in lice. The aim of this study was to detect alleles resistant to pyrethroids in the domain II (S5-S6) of the VGSC gene in goat biting louse. Goat biting lice were collected from five provinces in the west and northwest of Iran. Genomic DNA was extracted from goat biting lice and Bovicola (Damalinia) caprae species was confirmed by amplifying the cytochrome oxidase subunit I (COXI) gene. A fragment in the domain II (S5-S6) of the VGSC gene was amplified using the specific primers and the resultant polymerase chain reaction products were sequenced. Substitutions T917I, L920F, I927F, L928A, R929V and L930M were identified in the examined sequences. The results showed that all the examined lice had at least one mutation in their VGSC gene associated with pyrethroid resistance or new mutations. The presence of these mutated alleles in the VGSC gene may be due to the long-term and multiple use of pyrethroids against arthropods. Thus, the molecular detection of resistance to pyrethroid insecticides in goat chewing lice can help plot a kdr frequency map to enact effective policies to control caprine pediculosis.

Tests on the efficacy of amitraz, ivermectin and eprinomectin for control of lice in goats

Ectoparasitic infestations with Linognathus stenopsis and Bovicola caprae are a serious concern in goat farms, especially during the winter and spring. This study tested the efficacy of three modern insecticide drugs (ivermectin, eprinomectin and amitraz) applied via different routes for control of sucking and chewing lice in naturally co-infected goats. Each of drugs was tested on 30 goats. The animals from the first flock were treated with a single dose of ivermectin, applied subcutaneously at 0.2 mg/kg, the second one received a single spot on treatment with 1 mg/kg еprinomectin and the third flock was treated twice with amitraz, through spraying at a dose of 4 mL/1 L water. The results were evaluated before the treatments and at post treatment days 3, 14 and 60. On post treatment day 60, the application of ivermectin resulted in reduction of Bovicola caprae population by 73.05%, and for that of Linognathus stenopsis: by 92.70%. Eprinomectin demonstrated 100% reduction of both lice. The reduction of L. stenopsis and B. caprae caused by amitraz was by 92.20% and by 98.61% respectively. The macrocyclic lactone eprinomectin showed the highest efficacy (Р<0.05), was not toxic for goats and therefore, may be used as a treatment of choice for lice control.

Presence of Two Lice Species (Insecta: Phthiraptera) in a Goat (Capra hircus) from La Comarca Lagunera, Mexico: A Case Report

Phthirapteriasis or pediculosis is the name given to the lice infestation, that causes skin allergy, anemia, and transmission of pathogens. This case report describes the presence of two lice species in a goat from la Comarca Lagunera in Coahuila. The collected specimens were identified as Bovicola caprae and Linognathus africanus. This document represents the first report of these lice species parasiting goats in the southeasthern part of Coahuila, Mexico. Further research are required including a greater number of animals and farms in order to stablish the prevalence of these ectoparasites, establish control measures, as well as to determine its role in the posible transmission of diseases of public and veterinary health concern.

A field study on the efficacy of ivermectin via subcutaneous route against chewing lice (Bovicola caprae) infestation in naturally infested goats.

Caprine pediculosis is an ectoparasitic disease of great concern among goat farmers in India. It may be caused by either sucking lice or chewing lice; the latter one results in severe skin lesions, leading to production loss. This study evaluated the effectiveness of the macrocytic lactone drug, ivermectin, administered via subcutaneous injection, against chewing lice Bovicola (Damalinia) caprae infestation in naturally infested goats. The study was conducted on 20 goats with severe B. caprae infestation. Animals of group A (n = 10) were treated using a single dose of ivermectin (200 µg/kg body weight) subcutaneously and animals of group B (n = 10) underwent placebo therapy using normal saline. The animals were examined on days 0, 3, 7, 14, 21, 28, 42 and 56 for lice counts. There was 100% elimination of lice in all animals of group A and effective protection from re-infection remained at least for 21 days. Considerable improvement in haematological parameters was also observed by day 21. Based on this study, ivermectin injected via a subcutaneous route can be used effectively for the therapeutic and prophylactic management of chewing lice infestation in goats maintained under an extensive grazing system.

Effect of Tick and Lice on Some Blood Constitute and Trace elements of Local Black Goat in Sulaimani, Kurdistan Region of Iraq

In this study isolated 100 adult female of local black goat (Capra hircus) examined in spring and fall season for Tick and Lice investigations, then divided into two groups: 50 infested goats with ectoparasite and 50 non-infested goats. Three species of ticks (Rhipicephalus sanguinus, R. turanicus and R. bursa) and one species of lice (Bovicola caprae) were observed. Biochemical values (serum proteins and some trace elements) analyzed, in infested goats emerges decline in serum protein value 7.12±0.08 µg/dl, albumin value 4.12±0.03 µg/dl and increase of globulin value 3.04±0.09 µg/dl, in serum protein and globulin values shows not significance differences, while described highly significance differences in albumin value at p?0.01, when compared to control goats. In trace elements decline of zinc level 48.97±1.20 µg/dl and copper level 114.15±3.75 µg/dl levels with a highly significant differences at p?0.01 in infested goats when compare to control goats. It is observed that mixed infestation has much effects than tick or lice infestation on goats, which led to reduction in serum protein value 6.89±0.20 µg/dl, albumin value 4.11±0.09 µg/dl and raise in globulin value 3.10±0.11 µg/dl without any significance differences, also noticed insignificant declines in zinc level 45.67±2.40 µg/dl, while decrease in copper level 99.33±9.86 µg/dl significantly at p?0.05.

Mortality caused by aqueous extract of the leaves of Datura stramineus to goat biting louse, Bovicola caprae (Phthiraptera)

Extensive and indiscriminate use of organic lousicides is leading to environmental hazards i.e. persistence of residues, development of resistance and targeting of non-target beneficial organism. Hence, phytotherapy is emerging as effective tool for louse control, due to ecofriendly and biodegradable nature of plant extracts. In the present study the mortality and repellency caused by five concentration of aqueous extract of the leaves of commonly available Datura stramineus were tested against goat biting louse, Bovicola caprae. Fifteen percent concentration of extract prepared from leaves of aforesaid plant imparted 77% mortality and 66% repellency to goat biting louse.

Lice induced immuno-oxidative wreckage of goats

The present study aimed to evaluate the immuno-oxidative patho-biology of lice infestation in goats. Sixty goats were divided into five groups; sucking lice (Linognathus africanus) infested (Group 1, n=12), chewing lice (Bovicola caprae) infested-mild (Group 2, n=12), chewing lice (B. caprae) infested-moderate (Group 3, n=12), chewing lice (B. caprae) infested-severe (Group 4, n=12) and healthy control (Group 5, n=12). To assess the pathological changes, markers of oxidative stress (lipid peroxidation-LPO, reduced glutathione-GSH, superoxide dismutase-SOD, Catalase-CAT and total antioxidant capacity-TAC), the markers of immune status (Tumour necrosis factor alpha- TNF-α, Interleukin-10- IL-10, Transforming growth factor beta 1- TGF-β1, ratios of TNF-α/IL-10 and TNF-α/TGF-β1) and hemato-biochemical status were evaluated. Significant anemia, hypoglycemia, hypoproteinemia and hypoalbuminemia were observed in caprine pediculosis irrespective of the type of lice infested. Remarkably increased oxidative stress was observed in chewing lice infested goats and no significant changes in oxidative stress markers were observed in sucking lice infested goats. TGF-β mediated suppression of Th1 and Th2 immune responses was observed in sucking lice infested goats; whereas, a Th2 cytokine dominant inflammatory response was observed in chewing lice infested goats. From the present study, it may be concluded that sucking lice infestation produces remarkable immunosuppression and chewing lice infestation produces significant oxidative stress and inflammatory responses in goats.

Population levels of phthirapteran ectoparasites on the goats in Rampur (U.P.).

Out of the four phthirapteran species known to occur, only two were recovered from the goats in district Rampur (ischnoceran louse, Bovicola caprae and the anopluran, Linognathus africanus). As many as, 26.5% (n=250) of the goats examined were found infested with Phthiraptera. The prevalence on two sexes of goats remained similar (X2=0.013, P<0.05). However, lice were more prevalent on younger goats than adults and older ones (X2=9.78, P<0.05). The correlation between the prevalence and mean monthly temperature of Phthiraptera was found significant. On the other hand correlation between prevalence and humidity was found insignificant. As many as, 74.5% of the infested goats carried both the species while 25.4% exhibited single species infestation. The ischnoceran louse, B. caprae was comparatively more prevalent (18.4%) than the anopluran L. africanus (11.2%). The mean intensity (mean number of lice counted per square inch, at 20 anatomical sites) of B. caprae was comparatively higher than that of L. africanus. As far as, the population composition is concerned the females outnumbered the males in natural population. On the other hands, nymphs dominated over adults in natural population.

A study on prevalence and factors associated with ectoparasitism in goats of two agro-climatic regions in India.

The present study was aimed to evaluate the factors associated with prevalence of various ectoparasites among goats during winter season in two different agro-climatic regions of India. A total of 320 goats (Uttarakhand-208; Uttar Pradesh-112) were screened and evaluated for ectoparasitism and associated factors. The occurrence of ectoparasitism in goats was studied in relation with age, sex, breed, housing, agro-climatic region and system of rearing. Prevalence of ectoparasitism among goats of lower Shivalik region (Dehradun and Tehri Garhwal districts) of Uttarakhand and Bareilly district of Uttar Pradesh was 90.38 and 39.29%, respectively. The common ectoparasites observed were chewing lice (Bovicola caprae), sucking lice (Linognathus africanus), fleas (Ctenocephalides felis) and ticks (Haemaphysalis spp.). Among all the ectoparasitic infestation, pediculosis was the most common affection during the study period in both agro-climatic region; chewing lice in Uttarakhand and sucking lice in Uttar Pradesh. Agro-climatic region, breed, immune status, system of rearing and hygiene were highly affecting the prevalence and distribution of ectoparasites among goats. High prevalence of ectoparasitism in the study area warrants the need for formulating appropriate intervention strategies to improve control of ectoparasites and awareness among goat farmers.

Study on the prevalence of ectoparasite infestation of ruminanats in and around Kombolcha and damage to fresh goat pelts and wet blue (pickled) skin at Kombolch Tannary, Northestern Ethiopia

An attempt was made to study the prevalence of ectoparasite damage on live cattle, sheep and goats in and around Kombolcha town and on raw goat skin to assess their skin defect on processed wet-blue (pickled) skins at Kombolcha tannery, south wollo zone, North-Eastern Ethiopia. A total of 240 cattle, 175 sheep, 66 goats, were used to study the prevalence of ectoprasites on live animals as well as 344 fresh goat pelts and pickled (wet-blue) goat skins were used to assess skin defects. The result obtained from live cattle demonstrated a high prevalence of Amblyomma (28.33%) followed by Sarcoptes scabiei (23.75%), Boophilus (11.25%) Demodex (9.58%), Psoroptes (0.4 %), respevtively. The prevalence of ectoprasite infestation of live sheep revealed Mellophagus ovinus (sheep ked) (32.57%), Bovicola ovis (22.28%), Amblyomma spp (12.57%), Sarcoptes scabiei (14.28 %), Ctenocephaliedes spp (8.57%), Demodex (6.85%), Linognathus africanus (6.28%) and Boophilus spp (4%). The result from goats demonstrates a high prevalence of Sarcoptes scabiei (30.3%) followed by Linognathus stenopsis (9.09%), Amblyomma (4.54%), Ctenocephalides spp (3.03%), Bovicola caprea (1.51%) and Demodex (1.51%) in that order. Result obtained from fresh goats pelts revealed an over all high prevalence of Sacoptes scabie (53.29%) followed by Linognathus stenopsis (9.88%), Bovicola caprae (2.08%) and Demodex (2.08%). Examination of pickled (wet-blue) skins from follow-up skins show a high prevalence of scratch (74.25%) followed by “Ekek” (68.56%), scar (67.06%), processing defect (28.44%). “Ekek” (Typical scatter type cockle) was found to show a significant (P

ECTOPARASITOS EM CAPRINOS E OVINOS NO MUNICÍPIO DE MOSSORÓ, RIO GRANDE DO NORTE

Goats and sheeps present an ectoparasite diversity that may result in considerable losses in these animals productivity. Fifteen agrarian reform settlements were visited, with the purpose of identifying ectoparasites in goats and sheeps, in which scraping, direct exams, and auricle exsudate collections were carried out. From the 494 examined goats, 89.87% had ectoparasites, as well as 232 sheeps, 76.72%. The arthropods identified in the goats were: Bovicola caprae (80.76%), Rhipicephalus microplus (1.01%), Cochliomyia hominivorax larvae (0.6%), Psoroptes cuniculi (0.4%), and Ctenocephalides felis (3.23%), Amblyomma parvum (1.01%) and Linognathus stenopsis (0.2%) which were described for the first time in Brazilian northeast. Mixed parasitism of B. caprae with R. microplus (0.46%) and P. cuniculi with B. caprae (0.23%) was also identified. In sheeps, B. ovis (74.5%), R. microplus (0.86%), C. hominivorax larvae (0.43%) and A. parvum (0.43%) were the ones registered for the first time, in this species, in Brazilian northeast, besides the association of B. ovis with R. microplus (0.56%). There was no association between gender and age (P>0.05). The development of studies to evaluate the ectoparasite importance as a limiting factor to animal production becomes important. KEY WORDS: Goats, ectoparasite, sheeps.

First Records of the Louse Solenopotes binipilosus (Insecta: Phthiraptera) and the Mite Psoroptes ovis (Arachnida: Acari) from Wild Southern Huemul (Hippocamelus bisulcus)

Two species of Phthiraptera, Bovicola caprae (Ischnocera: Bovicolidae) and Solenopotes binipilosus (Anoplura: Linognathidae), and one species of mite, Psoroptes ovis (Acari: Psoroptidae), were recorded on huemul (Hippocamelus bisulcus) in Chile. The sucking louse S. binipilosus and the mite P. ovis are reported for the first time from this host.

Prevalence of lice infesting goats in Mosul

The aim of this study is to find the prevalence and diagnosis species of lice infesting goats in different seasons and different areas and farms in Mosul, and to determine the severity of infestation among 450 native goats during a period of one year. The result of the study revealed that 14.2 % of the examined goats harboured lice or their eggs (nits). Among the infested animals it was reported that 17% were considered as light, 38% moderate and 45% heavy degree of infestation respectively. It was found that the sucking lice Linognathus stenopsis was more predominating than the biting one Bovicola caprae (Damalina caprae). It was observed that the highest degree of infestation was in Winter. Mixed infestation was noticed. The clinical signs in infested goats were itching, emaciation, pale mucous membrane, restless and decrease milk production, hair loss or matted and rough haircut.

Variação estacional de Bovicola caprae parasitando caprinos no Estado da Paraíba

Os efeitos da temperatura, umidade relativa e precipitação pluvial na população de Bovicola caprae parasitando caprinos na região semi-árida do Estado da Paraíba foram avaliados de agosto 1999 a julho de 2002. Nos dois primeiros anos (agosto de 1999 a julho de 2001) 30 caprinos foram examinados, enquanto que 16 caprinos foram examinados no terceiro ano (agosto de 2001 a julho de 2002). Os animais eram mestiços adultos de ambos os sexos e foram abatidos para consumo humano no Matadouro Público de Patos, PB. As amostras de piolhos foram coletadas de três regiões anatômicas do corpo: maxilar, dorso e glúteo. O teste de Spearman (p&lt; 0.05) foi utilizado na tentativa de se estabelecer uma correlação entre a intensidade média de infestação de todos os estágios e o número total de cada estágio com os fatores abióticos. A prevalência variou entre 75 e 100% durante o período de estudo. O aumento da população de piolhos nos períodos de seca deveu-se provavelmente a nutrição deficiente dos animais em conseqüência da escassez de pastagem e manejo inadequado do rebanho em vez dos efeitos dos fatores abióticos.

Use of scanning electron microscopy to confirm the identity of lice infesting communally grazed goat herds.

Lice have been described on goats in commercial farming systems in South Africa but not from flocks on communal grazing. During a longitudinal survey on the causes of goat kid mortality, conducted in Jericho district, North West Province, lice were collected from communally grazed indigenous goats. These lice were prepared for and viewed by scanning electron microscopy, and micro-morphological taxonomic details are described. Three species of lice were found in the study area and identified as Bovicola caprae, Bovicola limbatus and Linognathus africanus. Sucking and biting lice were found in ten of the 12 herds of goats examined. Lice were found on both mature goats and kids. Bovicola caprae and L. africanus were the most common biting and sucking lice respectively in all herds examined. Scanning electron microscopy revealed additional features which aided in the identification of the louse species. Photomicrographs were more accurate aids to identification than the line drawings in the literature and facilitated identification using dissecting microscope.

Tests of Insecticides for the Control Goat Lice in 1957 and 1958 c

To investigate reports on resistance or goat biting lice ( Bovicola caprae (Gurlt) and B. limbatus (Gerv.)) to chlorinated hydrocarbon insecticides, goats from two ranches near Kerrville, Texas, were dipped into insecticides at dosages recommended by the Entomology Research Division, U. S. Department of Agriculture. Lice from one ranch were not killed by 0.25% toxaphene, which previously had been very effective. Field tests were conducted with sprays of Delnav® (2,3- p -dioxanedithiol S,S - bis( O,O -diethyl phosphorodithioate )), ronnel, malathion, Dipterex® ( O,O -dimethyl 2,2,2-trichloro-l-hydroxyethylphosphon- ate), Bayer 21/199 ( O -( S -chloro-4-methylumbelliferone) 0,0 - diethyl phosphorothioate), Sevin®(1-naphthyl N -methyl carbamate), and toxaphene for the control of biting lice and sucking lice ( Linognathus stenopsis (Burm.)) Toxaphene and 0.1% Delnav failed to kill lice. Others were effective within 24 hours on goats with fleece shorter than 10 weeks' growth, and from g to 5 days on goats with longer fleece. Flocks sprayed with 0.5% ronnel, 0.1% Bayer 21/199, and 0.5% Sevin were free of lice at the next shearing (2 to 4 months).