Acta vet. scand . 1992,33,387-390.

Brief Communication

Preliminary Observations on Naturally Acquired Hypobiotic oncophora Infections in

Many species, parasitic as well as ations of C.oncophora worm burdens were free-living, have the ability to ente r a hypobi• not included in the studies until the third time otic state of developm ent in the course of of slaughtering (February 2). Therefore, only their life cycle. Amo ng the parasitic nema• the recoveries from 8 could be pre• todes of cattle, perh aps ostertagi is sente d in Table 1. the most renowned in that respect, as the re• The following parasitological and immuno• sumed develo pment of hypobiotic larvae is logical parameters were monitored at 2 week thought to contribute to the Type II osterta• intervals: faecal strongylid egg counts (Hen giasis seen in early spring (Armour & Og riksen & Aagaard 1976), faecal cultures with bourne 1982). In contrast, only few reports subsequent larval differentiations (Hen riksen have been made on the occurrence of natural• 1972) and specific antibody responses of the ly acquired hypobiotic infections with Coop IgG 1 isotype. The latter were determined in eria oncophora (Brunsdon 1972). The present an ELISA according to the method describ ed experiment was originally set up to assess the by Canals & Gasbarre (1990). The employed occurrence in Denmark of hypobiotic parasite antigens were crude whole worm ex• O.ostertagi larval infections in young cattle tracts deri ved from adult worms of Cionco pastured on O.ostertagi contaminated fields phora. during autumn. However, in the course of these studies C.oncophora infection became evident, leading to the observations reported Tab leI . worm burdens reco• vered from 8 of the 12 group A calves at the sequen• here. tial killings. Two groups of parasite-free Jersey bullock Date c.one. Cone. calves were graze d for 6 weeks during Octo• Date adults larvae 'Total ber and November, 1989. One group (A), comprising 21 calves, was grazed on an Oios Feb. 2 66.7% 33.3% 900 tertagi and C.oncophora contaminated pas• 50.0% 50.0% 800 ture, while the other group (B), comprising 9 Mar. 1 88.9% 11.1% 1800 69.8% 30.2% 430 animals, grazed a non-contaminated pasture . Mar. 28 26.1% 73.9% 2300 In the course of the winter housing period 0.0% 100.0% 500 from November until April, 12calves of group Apr. 26 75.0% 25.0% 400 A were slaughtered (2 at a time) at monthly 0 intervals, and the worm burdens were as• Cone. =C.oncophora sessed according to the met hod described by *Total = The total C.oncophora worm burden of the Grenvold et al. (1989). However, determin- individual animals.

Acta vet. scand. vol. 33 no. 3 • 1992

10' 388 C. M. Christensen

Group A calves acquired a moderate initial nificantly above the control group (B) levels infection resulting in egg excretions declining soon after turnout on pasture in October 1989 from around 200 EPG in December to negli• (p<0.05; Bonferroni's t-test). Through the gible values in April. The results of the larval winter housing period, the IgG 1 levels consis• differentiations indicated that C.oncophora tently increased until the end of the experi• and O.ostertagi contributed approximat ely ment in late April (Fig. 1). At the sequential equally to the EPG values. However, these killings of group A calves moderate numb ers differentiations were not initiated until Janu• of both adults and larvae of C.oncophora ary 1990, and the preceding time cannot be ac• were recovered (Table 1). counted for. The anti-C.oncophora serum Although initially intended to be a study of

IgG 1 antibody response of group A rose sig- responses to only O.ostertagi infections, there

IgGl

1. 0 •

1 0 .9 , J 1 [:i 1 0 .8 j

J I o. 7 ·0 1 ·:; • j 0 .6 , j I 1 ! ,1

0 )

J i 1

0.4 j J j J 0.3 " llC7 a. - .. IlK .. All an ..

Figure 1. Serum IgG1 antibody response against Cooperia oncophora adult worm-antigen;expressed as group mean values of the absorb ance measured at 405 nm (for the 2 X 9 continuously kept calves of grp. A and B). Group A (e) exposed to parasites; group B (x) uninfected control s. ,J.. indicates the time of housing.

Acta vel. scand. vol. 33 no . 4 - 1992 Preliminary observations 389 was an admixture of C.oncophora to the pre• ed pastures, where they acquired substantial viously O.ostertagi mono-infected pastures, infections, when compared to the 'usual' late• thus allowing for a preliminary study of the season infection. occurrence of hypobiotic C.oncophora infec• More experiments should be carried out, em• tions in autumn-pastured cattle in Denmark. ploying predominantly C.oncophora contami• The presence of hypobiotic C.oncophora in• nated pastures, in order to properly assess the fections was indicated by the larval worm bur• proclivity of C.oncophora to enter hypobiosis dens recovered from the calves (see Table 1). in the course of naturally acquired infections. A continued presence of adult worms, pre• Additionally, the possible impact of such in• sumably as a result of the resumption of larval fections on the course of O.ostertagi hypobio• development, was further suggested by a per• tic infections and development of Type II os• sistent (although moderate) C.oncophora egg tertagiasis should be investigated. output throughout the housing period. Fur• ther indications were inferred by the continu• Acknowledgements ous rise in anti-C.oncophora serum IgG anti• I wish to thank professor, Dr. P. Nansen and Dr. J. 1 Monrad for their support of this work. Mr. N. Midt• body responses. When testing the same sera gaard and Mrs. K. Madsen are gratefully acknow• against O.ostertagi antigens, a significant in• ledged for their expert technical assistance. crease in anti-O.ostertagi IgG1 antibody levels was not apparent until March/April (unpub• CM. Christensen lished data). Department of Veterinary Microbiology, the Royal Veterinary and Agricultural University, 13 Billows• While the occurrence in Denmark of hypobio• vej, DK-1870 Frederiksberg C, Denmark. tic O.ostertagi infections leading to Type II os• tertagiasis has previously been reported (Hansen 1979), similar descriptions cannot be found for C.oncophora infections. However, References ArmourJ, Ogbourne CP: Bovine ostertagiasis: A re• the propensity of C.oncophora to enter hypo• view and annotated bibliography. Miscellaneous biosis has been described elsewhere for natu• publication No.7, Commonwealth Institute of rally acquired (Brunsdon 1972) as well as ex• Parasitology, Commonwealth Agricultural Bu• perimental infections (Borgsteede & Hendriks reaux, St.Albans, UK. 1982. Borgsteede FHM, Hendriks J: The possible relation• 1978). It has been concluded that, as for Oios• ship between the parasite generation and the tertagi, the environmental factors are of major ability of its progen y to interrupt the early para• importance for the induction of arrested de• sitic development. In: FHM Borgsteede (Ed): velopment in primary infections (Michel et al. Facts and Reflections III. Central Veterinary In• 1975). stitute, Lelystad , The Netherlands. 1981, p. 89• 100. The occurrence of arrested Cooperia may Brunsdon RlI.· Inhibited development of Ostertagia nonetheless be somewhat atypical. Immunity spp. and Cooperia spp. in naturally acquired in• towards Cooperia spp. will usually be built up fections in calves. N.Z. vet. J. 1972,20,183-189. within 2 months, i.e. fairly early in the grazing Canals A, Gasbarre LC: Ostertagia ostertagi: Isola• season, thus preventing large numbers of lar• tion and partial characterization of somatic and metabolic antigens. Int. J. Parasit. 1990,20, 1047• vae (including those that are inhibition• 1054. prone) to become established later on (Coop Coop RL, Sykes AR, Angus KW.· The Pathogenicity et al. 1979). However, in the present case sus• of Daily Intakes of Cooperia oncophora Larvae ceptible animals were set out on contaminat- in Growing Calves. Vet. Parasit. 1979,5,261-269.

Act a vet. scand. vol. 33 no. 4· 1992 390 C. M. Christensen

Gren vold J, Henriksen SAa , Nansen P, Wolstrup J, McMaster method). Nord. Vet.-Med. 1976, 28, Thylin J: Attempts to control infection with Os 392-297. tertagia ostertagi () in grazing Henriksen SAa : Undersegelser vedrerende lebe• calves by adding mycelium of the nematode• tarmstrongylider hos kvreg. 1. Nogle forelebige trapping fungus Arthrobotrys oligospora (Hy erfaringer med L3-analyser. (Investigations con• phomycetales) to cow pats. J. Helminthol. 1989, cerning bovine gastro-intestinal strongyles. I.

63,115-126. Preliminary results of L3-analyses). Nord.Vet.• Hansen Jw" Type II ostertagiose (Vinterostagiose); Med.1972,24,49-55. En oversigt. (Type II ostertagiasis (winter Michel JF, Lancaster MB, Hong C: Arrested devel• ostertagiasis); A review.) Dansk VetTidsskr. opment of Ostertagia ostertagi and Cooperia on 1979,62,233-239. cophora. Effect of temperature at the free-living Henriksen SAa, Aagaard K: En enkel flotations- og third stage. J.comp.Path. 1975,85,133-138 . McMastermetode (A simple flotation and

(Received July 9,1992; accepted August26,1992).

Reprints may be requested from: C. M. Christensen, Department of Veterinary Microbiology, Royal Veterina• ry and Agricultural University, 13 Bulowsvej, DK-1870 Frederiksberg C, Denmark.

Acta vet. scand. vol. 33 no. 4 - 1992