Efficacy of anthelminthic control programs against natural muellerius capillaris infection in sheep in the north-west of spain. effect on blood gases and ph in venous blood samples

Efficacy of anthElminthic control programs against natural
Muellerius capillaris infEction in shEEp in thE north-wEst of spain.
EffEct on blood gasEs and ph in vEnous blood samplEs
LóPez C.M., Cienfuegos s., DaCaL V., Vázquez L., PanaDeRo R., feRnánDez g., Díaz P., Lago n., Díez-baÑos P. & MoRRonDo M.P.* Summary:
Résumé : Efficacité dE différEnts anthElminthiquEs vis-à-vis dE
l’infEction naturEllE par Muellerius capillaris d’ovins dans lE nord-
The field efficacy of a single dose treatment against natural ouEst dE l’EspagnE. EffEts sur lEs gaz du sang Et lE ph vEinEux M. capillaris infection using different anthelmintic drugs, extensively L’efficacité sur le terrain d’un traitement à dose unique par différents employed in ovine parasite control programs in Galicia anthelminthiques vis-à-vis de l’infection naturelle par M. capillaris (N.W. Spain), and the effect of protostrongylid infection on ovine d’ovins en Galice (Espagne), ainsi que l’effet de cette infection sur respiratory functions, were evaluated. Five groups (n = 5) of ewes la fonction respiratoire de ces ovins ont été évalués. Cinq groupes were used in this study; animals were treated with injectable (n = 5) de brebis ont été utilisées dans cette étude. Les animaux ont ivermectin (0.2 mg/kg), levamisole (7.5 mg/kg) and albendazole été traités soit avec de l’ivermectine injectable (0,2 mg/kg), soit du (5 mg/kg) and monitored at 0, 7, 21, 42 and 63 days post- lévamisole (7,5 mg/kg), soit de l’albendazole (5 mg/kg), et la treatment (d.p.t.) by enumeration of the lungworm larvae per gram charge parasitaire a été mesurée à 0, 7, 21, 42 et 63 jours post- of faeces (l.p.g.) and determination of gas tension and pH in traitement (j.p.t.) par la détermination du nombre de larves par venous blood using an i-Stat portable clinical analyzer. No gramme de fèces (l.p.g.) et par la mesure de la pO2, de la pCO2 statistical difference was found either in larval elimination between et du pH dans le sang veineux à l’aide d’un i-Stat analyseur untreated and treated groups or in the reduction in larval counts in clinique mobile. Aucune différence statistique n’a été retrouvée pour all of the treated groups. A significant increase in partial oxygen ce qui concerne le nombre de larves présentes entre groupes traités tension (pO2) and saturation (sO2) between day 0 and 7 p.t. was et non traités. Des augmentations significatives de la pression observed in all treated animals. These values decreased significantly at day 21 to previous levels. There were no statistical 2) et de la saturation (SO2) entre les jours 0 et 7 p.t. ont été observées chez tous les animaux traités. Au-delà de differences in blood gases between uninfected and treated groups. 21 j.p.t., ces valeurs sont revenues aux valeurs d’avant traitement. We can conclude that under Galician field conditions, parasitic Nous pouvons conclure que, dans des conditions réelles en Galice, control programs are not totally effective against M. capillaris les programmes de contrôle des parasites ne sont pas efficaces contre l’infection par M. capillaris. KEY WORDS: sheep, Muel erius capil aris, treatment, field efficacy, blood gases.
MOTS CLÉS : ovins, Muellerius capillaris, traitment, efficacité sur le terrain, gaz
in galicia (north-west of spain) sheep are raised protostrongylid infection is not very common in sheep, mainly in a semiextensive husbandry system. in this Valero et al. (1992) and berrag & Cabaret (1996) found region, mild temperatures and environmental humi- that heavy infections decreased carcass weights, dity are optimal for the survival of many important increased levels of mortality and impaired pulmonary livestock parasites, such as small lungworms (Protos- trongylidae). Neostrongylus linearis, Muellerius capil­ in this study the field efficacy of three anthelmintic drugs laris, Cystocaulus ocreatus and Protostrongylus sp. are (albendazole, levamisole and ivermectin) against M. the species parasitizing sheep in galicia (Díez-baños et capil laris natural infection, using protocols extensively al., 1994), although a recent extensive survey carried used in ovine parasite control programs, was evaluated, out by Cienfuegos et al., (2007) have shown Muellerius together with the effect of natural infection by M. capil­ capillaris as the most frequent lungworm, with 98.2 % laris and the subsequent effect of treatment over pulmo- prevalence over the rest of the species and a mean of nary gas exchange under natural conditions.
larval shedding of 67.4 ± 297.7 larvae per gram of faeces (lpg). although clinical disease associated with * Parasitology and Parasitic Diseases. animal Health Department. Lugo Veterinary faculty. santiago de Compostela university. 27002, Lugo, spain.
Correspondence: Ceferino M. López.
Tel.: +34-82252231 - fax: +34-82252195.
in March 2008, 25 ewes from Lugo province were examined twice by means of the baermann-Wetzel technique (baermann, 1917; Wetzel, 1930) in order LóPez C.M., Cienfuegos s., DaCaL V. et al. to confirm a natural pure infection by M. capillaris. sheep grazed pastures around the farms during the day and were housed at night in strawed-floor stables. sheep Larval elimination was transformed to the logarithm of included in this study were ewes (> 3 years) that have the count plus 1 to calculate geometric means. To assure not received any anthelmintic treatment during the last homogeneity of sheep groups, larval counts in day 0 year (last treatment March-april 2007).
were compared using Kruskal-Wallis non parametric The ewes were ranked according to larval shedding analysis. Differences in larval excretion at day 7, 21, 42 before treatment. Within ranks, sheep were randomly and 63 p.t. were analyzed using Mann-Whitney test to compare the treated groups with the positive untreated - group 1 (n = 5), untreated control group.
one. The significance in reduction of larval counts over - group 2 (n = 5), treated with injectable ivermectin time was tested with friedman non parametric test for 1 % for ovine at the dose rate of 0.2 mg/kg body weight sc (ivomec®, Merial Ltd. essex, england).
The effect of the treatment over gas tension and pH in - group 3 (n = 5), treated with levamisole base (hydro- treated animals was analyzed with repeated measures chloride) 7.5 % at a dose rate of 7.5 mg/kg b.w. sub- anoVa. “Repeated” contrast was introduced to deter- cutaneously administered (Caliermisol®, Laboratorios mine if measures were significantly different from the adjacent sample. “simple” contrast was used to compare - group 4 (n = 5), treated with albendazole 2.5 % at a between groups measures. all the analysis were realized dose rate of 5 mg/kg b.w. per os (ganadexil®, inVesa with sPss, Version 15.0.1, sPss inc., 1989-2006).
industrial Veterinaria s.a., barcelona, spain).
We also included a negative control group, composed by five ewes with no larval elimination in two succes- sive samplings (group 0).
after treatment, animals were maintained under field conditions, so that reinfections were possible.
The geometric mean of lpg and the statistical signi- fication between untreated and treated groups faecal and blood samples were taken before treatment are shown in Table i. all the animals of the posi- (day 0), and at 7, 21, 42 and 63 days post-treatment (d.p.t.). tive control (g1) and treated groups (g2, g3 and g4) faeces were collected directly from the rectum with plastic were positive previously to treatment. neither statistical gloves and were kept cool until being analyzed by the difference was found between untreated and treated baermann-Wetzel technique in the same day.
groups during the study nor in the reduction in larval blood samples were collected from the jugular vein into counts all through the study in all of the treated groups.
Lithium-heparin vacuum tubes (bD Vacutainer®, becton, all larvae recorded throughout the study were identified Dickinson and Company) and were immediately ana- lyzed for blood gas tension and pH, using the i-sTaT portable clinical analyzer (i-sTaT Corporation, east Windsor, usa). The following parameters were mea- sured: pH, partial pressures of o2 (po2) and Co2 (pCo2), Results of blood gas tension and pH of infected (g1-g4) oxygen saturation (so2), bicarbonate concentration and uninfected (g0) groups are shown in Table ii. all (HCo3), total Co2 (TCo2) and base excess (be – amount treated groups (g2-g4) were considered as a whole of H+ required to returned blood pH to reference value).
(gT) because of the lack of statistical differences in Animal group*
* g1: untreated group; g2: ivermectin treated group; g3: levamisole treated group; g4: albendazole treated group.
Table i. – geometric Mean lpg and Median (between brackets) in the different groups of sheep.
anthElminthic control programs against protostrongylids Variable
21 d.p.t.
42 d.p.t.
63 d.p.t.
* Repeated Measures anoVa (Repeated Contrast) p < 0.05 Po2 and so2 7 days vs 0 days and Po2 and so2 21 days vs 7 days.
Table ii. – arithmetic mean ± standard deviation of pH and blood gas tension of the uninfected (g0), positive control (g1) and all treated groups (gT) measured using the i-sTaT portable clinical analyzer.
larval elimination. using a repeated measures anoVa Most anthelmintic treatments have shown an important with “Repeated” contrast, significant increase in partial lack of efficacy against protostrongylid lungworms, and in particular against M. capillaris (bliss & greiner, 1985; day 0 and day 7 p.t. (f = 7.055; p = 0.019 and f = 7.076, McCraw & Menzies, 1986; Helle, 1986; Díez-baños et p = 0.019, respectively) were observed in gT. These al., 1995; Rehbein & Visser, 2002). some of those values decreased significantly at day 21 (f = 5.003, authors found that Muellerius larvae reappeared in fecal samples in less than 60 days, even in animals under previous levels. The “simple” contrast did not shown strict isolation. This reappearance might be explained statistical differences between treated groups (gT) vs by immature Muellerius forms, not affected by anthel- untreated parasitized control group (g1) or negative mintic treatment, developing to maturity after destruc- tion of the original adult population (McCraw & Menzies, 1986, 1988) or by the protection conferred by altered tissue surrounding that lungworm that is more pro- nounced than in other protostrongylid species (Rehbein & Visser, 2002). Recently, Papadopoulos et al. (2004) and geurden & Vercruysse (2007) have obtained better one of the treatments that are usually employed results with moxidectin and eprinomectin, respectively, in ovine parasite control programs in galicia but in those cases larval elimination was studied for a was completely effective against M. capillaris. short period of time after treatment, giving no time for Despite a temporary descent in larval elimination the reappearance of larvae observed in other studies.
detected in all groups, at least one animal were elimi- in galicia, traditionally parasite control practices in nating larvae in faeces at every sampling time and most ovine include a systematic single dose treatment in of them shed larvae at the end of the study (63 d.p.t.).
spring and/or autumn, mainly with benzimidazoles LóPez C.M., Cienfuegos s., DaCaL V. et al. (bzD), that generally it is designed to control gastro- intestinal nematode infections. However, specific treat-ment for protostrongilyd infections would require higher dosage than these (Richard & Cabaret, 1992) or repeated The authors thanks to oViCa (galician association of ovine and caprine breeders) and the veterina- treatments (McCraw & Menzies, 1986).
rians of the aDsg aCiVo for their collaboration blood gas tension and pH were obtained from venous in the realization of this study. This work was supported samples with a portable clinical analyzer to reproduce by the research project PgiDiT06Rag26101PR.
the field clinical conditions. Though blood gases and pH are usually measured in arterial blood, according to garcía alarcón et al. (2003) and Dascombe et al. (2007) venous values reflect correctly and can be used to eva- luate the pulmonary gas exchange, particularly when values are used for comparative purposes (Verwaerde baErmann g. eine einfache Methode zur auffindung von anky- lostomum-(nematoden)-Larven in erdproben. Geneesk. The treated group (gT) was not significantly different tijaschr. Nederl.­Indië, 1917, 57, 131-137.
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