Prevalence of some internal parasites found (1971–1989) in horses born on a farm in central kentucky

Prevalence of some internal parasites found (1971–1989) in horses born on a farm in central kentucky

LJ Refereed PREVALENCEOF SOME INTERNALPARASITESFOUND(1971-1989) IN HORSES BORN ON A FARM IN CENTRALKENTUCKY E. T. Lyons, PhD; J. H. Drudge, DVM, ScD ...

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LJ Refereed

PREVALENCEOF SOME INTERNALPARASITESFOUND(1971-1989) IN HORSES BORN ON A FARM IN CENTRALKENTUCKY E. T. Lyons, PhD; J. H. Drudge, DVM, ScD and S. C. Tolliver, BS

SUMMARY

Prevalence of several species of naturally acquired internat parasites are reported from a total of 97 horses (mostly mixed lighthorse type) from a farm in central Kentucky. The horses were born and raised in 2 adjacent fields (No. 4 - n--44 and No. 10 - n=53) over a 19-year-period (1971-1989). They were 100 to 537 days old (av. 281) when examined; an exception was a 819-day-old not calculated in the average age. Some of the horses were not examined for all of the parasites. These horses (never previously treated) were all used in critical or controlled tests for evaluation of antiparasitic activity of drugs. Dams and other horses in the fields rarely were given an antiparasitic compound. Prevalence and aggregate mean numbers of parasites in infected animals (in parentheses) for the 97 horses are: bots Gasterophilus intestinalis 2rid instar, 65%(45), 3rd instar, 96%(210), Gasterophilus nasatis 2nd instar, 18%(10), 3rd instar, 63%(10); stomach worms - Habronema muscae, 73%(78), Draschia megastoma, 42%(53); ascarids - Parascaris equorum mature, 75%(45), immature 36%(29), tapeworms - Anoplocephala perfoliata, 33 % (7); large strongyles - Strongylus vulgaris, 95%(80) (data on horses >180 days old), Strongylus edentatus, 94%(34) (data on horses >330 days old); pinworms - Ox3,uris equi, 43%(87); eyeworms -

Authors' Address: Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099 (U. S. A.} ACknowledgements: This investigation was conducted in connection with a project of the Kentucky Agricultural Expe rimen t Station and is published with the approval of the director as paper No. 89-4-37.

Thelazia lacrymalis, 61%(6); S. vul garis in cranial mesenteric artery, 92%(53); and S. edentatus in ventral abdominal wall, 98% (56). Differentiation was made for the data by season and by age of the horses when they were examined. Information from this research reflects the transmission patterns and prevalence of these parasites under natural conditions.

INTRODUCTION

Parasite control program s are generally excellent on major horse farms in the United States. Baseline data on transmission patterns and prevalence of internal parasites of equids under any circumstances are sparse. The main purpose of this paper is to present data on internal parasites recovered from horses over a 19-year-period on a farm in central Kentucky where animals in 2 fields were not on a routine parasite control program. Additionally, the research was undertaken to obtain data on transmission of internal parasites in equids in Kentucky relative to season and to age of the horses. Comparison of these data with previous surveys of internal parasites of equids in Kentucky was also a goal.

MATERIALS AND METHODS

The data in this paper are from horses used in evaluation of activity of antiparasitic compounds in critical or controlled tests. Before thes e tests, none of the horses received chemotherapy for internal parasites. All horses (n=97) were born in 2 adjacent fields - No. 4 (n=44) and No. 10 (n=53) between 1968 and 1988 and killed between 1971 and 1989. Field No. 4 consists of about 2 hectares and Field No. 10, about 10

L

Volume 10, Number 2, 1990

99

T a b l e 1 . P r e v a l e n c e of natural infections of internal parasites in h o r s e s o n a farm (Field No. 4) in central K e n t u c k y ( 1 9 7 1 - 1 9 8 9 ) Horses Parasite species

No. examined C; ©

Total

No. inf

Prev (%)

No. parasites in infected horses Range

AMN*

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SMALL INTESTINE

Parascaris equorum: Mature Immature

Anoplocephala magna

25 25 25

19 19 19

44 44 44

32 14 1

(73) (32) (< 1)

1-370 1-250 1

45 34 1

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VENTRAL ABDOMINAL WALL

Strongylus edentatus

16

11

27

26

(96)

1-66

23

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hectares. Both fields had breeding bands of horses consisting of 1 stallion and varying numbers of mares, fillies and foals. For Field No. 4, the number of mares and fillies ranged from 2 to 4 from 1971 to 1978, and 4 to 7 from 1979 to 1989. The numbers of mares and fillies in Field No. 10 varied from 5 to 9 from 1971 to 1978 and from 9 to 17 from 1979 to 1989. The majority of the original breeding animals (and therefore the parasites) were from the same source of horses in other fields on the farm. Foals born to mares in both fields were usually killed for drug tests, but some females were left for replacement breeders. Essentially, both fields were closed Systems, but occasionally, an adult horse was added for replacement, especially in Field No. 10. The only antiparasitic treatment of any of the breeding stock since 1979 has been medication of replacement animals. The foals were born between March and October (an exception was 1 in February) and approximately 60% were born in April and May. Ages of the horses when killed were from 188-819 days (Field No. 4) and 100-486 days (Field No. 10). For the 97 horses examined, the numbers varied from 1 (1971; 1972)to 11 (1989)per yearand from 1 (August)to 17 100

(January) per month for numbers combined for each month of the 19-year-study. The sire and dams in Field No. 4 were mixed lighthorse. In Field No. 10, the sire was usually Thoroughbred and the dams were mostly mixed lighthorse, with a few being Thoroughbreds. The large intestines of all horses were examined for Strongylus vutgaris and Strongylus edentatus; however, data are presented in tabular form only for those horses theoretically old enough to harbor mature S. vulgaris at > 180 days and S. edentatus at >330 days-of-age. Data were collected for each parasite in all 44 horses in Field No. 4 except for eyeworms (n=25), S. vulgaris in the cranial mesenteric arteries (n=41), and S. edentatus m the large intestines (n=18) and in the ventral abdominal wall (n=27); and in all 53 horses in Field No. 10 except for eyeworms (n=28), stomach worms (n=19), S. vulgaris in the large intestines (n=42) and in the cranial mesenteric arteries (n=40), and S. edentatus in the large intestine (n=12) and in the venlral abdominal wall (n=19). Methods for recovery of the internal parasites from the

EQUINE VETERINARY SCIENCE

Table 2 . Prevalence of natural infections of internal parasites in horses on a farm (Field No. 10) in Central Kentucky (19711989).

Parasite species

O"

Horses No. e x a m i n e d © Total

No. inf

Prey (%)

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No. parasites in infected horses Range AMN*

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36 36 12 12

17 17 7 7

53 53 19 19

13 34 15 7

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1-43 1-50 1-161 4-158

12 13 28 57

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36 28 10 36

17 14 2 17

53 421" 121"1` 53

15 41 12 27

(28) (98) (100) (51)

1-79 4-703 15-238 1-758

6 152 65 115

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27

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39

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2-399

62

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"AMN = Aggregate mean number (Total No. of parasites found ÷ Total number of infected horses). 1 Only data on horses _>180days old are presented; however, 3 specimens were found in 1 horse at 136 days of age. 1"1.Only data on horses _>330days of age are presented; however, 1 to 4 specimens were found in each of 7 horses at 256 to 319 days of age. No. int. = No. of horses infected; Prey (%) = Prevalence (%).

horses and other procedures have been reported previously.l,~3,4.5.6

RESULTS AND DISCUSSION

Prevalence and number of internal parasites in horses in Field No. 4 (Table 1) and in Field No. 10 (Table 2) are recorded. Rates of infection for the various parasites tended to be somewhat higher in Field No. 10 horses than in Field No. 4 horses. The differences did not exceed 20% except (about 30%) for Gasterophilus intestinalis 2nd instar and Thetazia lacrymalis. Similarly, the aggregate mean number (AMN) of parasites in infected horses also was overall higher in horses from Field No. 10; particularly for G. intestinalis, large slrongyles, and pinworms. Data on prevalence and A M N for parasites combined for horses in both fields are appropriately compared to those recently published in 1987 for horses (n=200 to 513) in a 2 8 year-period in Kentucky? For parasites in the present study, Volume 10, Number 2, 1990

compared to the 1987 paper, 9 prevaiences differed <20%. Also, A M N of parasites were higher for 3rd instar G. intestinalis, m a t u r e P a r a s c a r i s equorum, and Oxyurls equi, but were lower for the other parasites. Prevalence and A M N for parasites have been combined for horses in both fields and are presented by season (Table 3) and by age of the horses (Table 4). Seasonal (spring, summer, fall, winter) differences were obvious for most of the parasites (Table 3). Bets are considered first and Jresent data will be compared with that published in 1975 on seasonal (monthly) transmission of these parasites in 476 horses in Kentucky over a 22-year-period (1951 to 1973). z Second instar G. intestinalis were more prevalent in the winter and the A M N was highest in the fall. For G. intestinalis 3rd instars, both the prevalence and A M N were highest in the spring and winter. These findings on G. intestinatis were similar to the 1975 report 2 where prevalence and A M N were highest for 2rid instars in December and for 3rd instars in February to April and in March and June, respectively. Gasterophilus nasalis 2nd instars were not present in the 101

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~i~i~iii~i~i!iii!iiiiiii!iii!iiiiiiiiii~i~iiiiiiiiiiiiiiiii!~iiiiiii~i!iii!i!i!iiiiiiii~iiiiiiiiiiiiii~i~~ii~iiiiiiii~iii!!iiiiiiiii~i~i~ii~i~iiiiiiiiiiiiiiiii!iiiiiiiii~iii~iiiiiiiiiiiiiii~iiii~iiiiiii!iiiiiii

lsom oaota ~.lVStm D aelsm. PLTq.I. "IleJ

was found in only I horse in the present study. For the eyeworm, Thelazia lacrymalis, the highest prevalence was in the winter and spring months, but the AMN was greatest in the summer. Results of examination of eyes of 189 Thoroughbreds (1 to 4 years old) at necropsy in Kentucky for the 1-year-period, March 1, 1984 to February 28, 1985, were published in 1986. ~ For these horses, prevalence of T. lacrymalis was highest in November and February. Prevalence of Habro nema muscae was highest for spring, summer and winter months; whereas, the highest AMN was in the fall. Draschia megastoma were most prevalent in the summer and the AMN was greatest in the fall. In the 1983 publication6 on 363 horses in Kentucky, prevalence and AMN were higher for H. muscae in December and June, respectively, and forD. megastoma, in May and November, respectively. Prevalence for both S. vul garis and S. edentatus in the large intestine was similar (Table 3 continued). For both parasites, prevalences were _>94% for spring, fall and winter and 82% (S. vulgaris) or 88% (S. edentatus) in the summer. The AMN was highest for both parasites in the spring, although the numbers ofS. edentatus were nearly as high in the fall. Comparable seasonal data for these 2 species of large sl~ongyles are not available in horses in Kentucky. Examination of the cranial mesenteric arteries revealed S. vulgaris to be most prevalent in the horses (>180days-old) in winter and fall and the AMN greatest in the winter. In the 1985 paper7 (March to February study) on S. vulgaris found in the cranial mesenteric arteries, the highest prevalence and AMN were in January. Strongylus edentatus were prevalent in the ventral abdominal wall of 100% of the horses (_>330-days-old) examined in the spring, fall and winter; AMN was highest in the spring. No comparable seasonal study of these forms has been done in horses in Kentucky. Volume 10, Number 2, 1990

Table 3 continued. :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

<.,.....+:+:.+:,.:..

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=============================================================::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ========================================== :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :i:ili:

::::::::::::::::::::::::::::::::::::::::::::~:::::::::::::::::::::::::::~(~}::::i~::i~::iiiiiiii~i.ii::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

~it~}i~!ti1=~i~1~:i~:i~i::~1::~;:~i~i:~:~i:~i~i~iitti::~::i~i::i~i~;~i:~i~ii;;~:;~:~i~;:~i:~i~ii~iiiiiiiiiii::~i~iiiiiiiiiiiii;~iiiiiii~i~i~i~iiiiiiiii~i~iiiiiii~iiii~;;~i;iii~iiiiiiitiiii~iiiii~i~i~1~ii~:;;~ Tl~elazia I ~ c ~ a l i $ Season

SPRING Mar-Apr-May SUMMER Jun-JuI-Aug FALL Sep-Oct-Nov WINTER Dec-Jan-Feb All Seasons

No. exam

No. inf (%)

Range

18

11 (62)

1- 11

4

9

2(23)

1-18

10

4

2(50)

1-6

4

22 53

17(78) 32(61 )

1-24

7 6

AMN

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=========================================================== i}}ii !i i ::ii!i::!:ii i::::::i::i::ili i :iiiiiiiiii:::: :::::::i:: i ::iiii::i::ii!i i!i i i i i i i i~i i !i!i !::!i!!!::i::i ~i i i ii::iiii~i i i ::::i ::::ii::!i!i i i i i i::i;i::ii i ::ii i::i!ii!i!iii::ii i ::::i::ii::iiiiii ii::ili!il;i!iii!!i!::i i iii i ililii ::::!! iii ~iii:::: ~j~ili[ i i i i i i:: !::ii :::::::::::::::::::::::: ~i:::~:::: ~~ ========================================================================================================= ~:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ~

:::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::: i ::: :i: :~i~~:::ii::ii:: : ::i::i~i::i~i:}:i::i~i::i ::~!i~::ii ~:i~i~i~i~i~i~i i i i i::ii !~!~i~i i ::i~i i ii~i:i:ii~i~ii~i~!ii}~i:i:i!~::i i i ii:i:~::i : i~i~i~i~i~i~i~:i~i: if:i~i~iiii~:i: iii~i~i~i~i~i: i~i~i~i~i::i~i~i~:i: ii: ~: i: ~iii ::i!i!!!!ii i i :.ii!::ii!i!!ii~iii~i~i::iiiiiiiili!::!::i!!~i~i~i~i~!!!iiiii!i!iiiiiii~i~i~ ii i i ~!!~!::~::~ii~?:!ii::i::i::ii !i::~!i!~i~::~::~::~i~i~::~::~ii !t!!ii~i~i!!!ii~!~!!!!~!~!i~i i !i!i~!!~i?:ii ~ i ~

~i i:~: i

i ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

~i;::i:: ::i=::!~i :t::ii:~:i}iiti! ::i::i::i~i ::i::i::;::i::i=i:i::;:i~:=i~i=i::l ~i=:i::i:=i::i:i:i~::ii;~i;i~i i:~i:=;~ii:~:::ii ::ii::i:;i;!i;}i~i~iiiiiiiiiitittttti!i l; i;iil;il;iiiiiiii!iii}ii ;i!;ii !i £i ;iiliiii i il::i}i::}~i =:: i: ii~ii: i=i:i~:i:i~:iiiiiiiiiiiiiiiiiiiiiiil}i =i : iii!iiiii!iiiiiii Dra.schia megastoma

Season SPRING Mar-Apt-May SUMMER Jun-JuI-Aug FALL Sep-Oct-Nov WINTER Dec-Jan-Feb

All Seasons

No, exam

No, inf (%)

Range

AMN

21

6(29)

1-158

60

9

6(67)

17-73

37

7

3(43)

1-373

148

26

11 (43)

4-90

3:3

63

26(42)

i i i if! !i!iiiiiiiiiiiiii!iii!!iiii!

53

! !iii~!~i~iiiiiiiiiiiiiiiiii~iiiiiiiii iiii~

ii~!!i

i i i iiii!iiiiiiiiiiiiiiiiiiiiiiiilili!!!ii!iiiiiii i i iiiii~iiiiii!iiiiiiiiiiiiilil

:i:iii:i:i:iii:i:iiii:iiiiiii:i:i:iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii:i:iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii

~i~i~i i i i i i i i ~i i i ~i i i i i!i~i ~!!ii i i i i i i i i i i i i i~i~!ii !!ii i~i i i~i i i i i i i~i ~!!ii !i ~i i i i i!i !!i!i i i~i i i i i i i i i i i MM~i!!i~!:::ii::ii::iii::ii;J~iiiiii!ii::~i::~i::i~i::i~!ii::::~::i!i!ii!iiiiiiiiii::i~iiiii!i~iii~i~i::i~iiiiiiii::iii::i:.iiiii~i~i~ii~iiii~iiiiiiiiiiiiiiiiii::i~iiiiiiiiiiii~ii:~ii::::::::::::::::::::::::::::::::::::

103

Table

3

Data arranged by age of the horses show various differences for the parasites (Table 4). Comparison of data on most of the parasites in this study will be made with those in the previously mentioned 1-year-study of 89 Thor-

continued Cranial MesentericArtery

Strongylus vulgaris Season

No. exam

No. inf (%)

Range

AMN

oughbreds examined at 14 to 333 daysof-age and published in 1985. 7 Para26 23(89) 2-111 28 sites in the 27-month-old horse in the 11 9(82) 1-40 13 present study will not be discussed because of its vast difference in age 16 15(94) 1-205 69 from the other horses. 28 27(97) 4-399 80 Prevalence and AMN were high81 74(92) 53 est for 3- to 6-month-old horses for i;;ii ililil;i!i i i i;ii;l;i i li;ilililil;ii;i i i ili;i;i i ilili;i ii i i;ii; iliil;; i ~ i l i ~ i ~ i l i ~ i i l i ;il;i;i;i;i;ii;;i;i i i i i;ilili i i i iilii iiiiiiii!!iiiiii~iiiiiliililiiii~i~i~ii~iii~i~!!!ii!~i!i!i~ii~ii~iiliii 2rid instar G. intestinalis and G. na~i~;i~iiiiii~iii~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~ii~f~iiiii~iiiiiiiiii~iiiiiiiiiiiiiiiiiiiiiiiiiiii~iii~ii::iii::iiii~::i::~::~!i~i~::~!~ii~ii~i~iiiiiiiiiiiiiiiiiii salis. The highest prevalence of 3rd instar G. intestinalis was for 6- to 12month-olds and of G. nasalis was for :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::: 12- to 18-month-olds. AMN was high~d~::i::;::i::i::~::~i~::i::~::i!iiiii:~::;::;::i::i::i::ii;::ii~::i::iii::i::i::i::iiiiii!i!iiii::ii;::;::i::~::!::~i~::~i~i~::~i~::~i~::~i~::~i~::::::::::::::::::::::::::::::::::::::::::::::::::::::~i~::~::~::~::~::~i est for 3rd instar G. intestinalis in 9 to ~ii~!iii!~iiii~iiii~iii~iiiiiiiiiiiii~iii~iiiiii~-~iiiiiiiiiiiiiiii~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~i~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~iii~iiiiiiiii~iiiii 12 month-old horses and for G. nasalis ~i~i:=iiiiiiiiiiiiiiii ~iiiiiiiiiiiiiiiii~~iiiiii~i~i;ill iiiiiil i~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii i;iiiiiiiliii!iiiiiiiiiiiiiiiiiiiiii!ii::i::i::i::i::i~i~i~ in 3- to 6-month-olds. In the study ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::iiii::ii : ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: published in 1985,Thighest prevalence and AMN for G. intestinalis 2nd and 3rd instars were in 9- to 12- and 6- to 9*No. exam= No. of horses examined. 1 No. inf. = No. of horses infected; (%) = Prevalence. 1"1"AMN= Aggregate mean number (Total No. of parasites found ÷ Total No. of infected horses.) month-olds, respectively. In the same §Only data on horses >180 days old are presented; however, 3 specimens were found in 1 horse at 136 study, 7 for G. nasalis, highest prevadays of age. ¶Only data on horses _>330days old are presented; however, 1 to 4 specimens were found in each of 7 lence for 2nd instars was for 3- to 6horses at 256 to 319 days of age. month-olds and for AMN was for 6- to 9-month-olds. Both values for G. nasalis 3rd instars were highest for 6- to 9-month-olds. T a b l e 4 . Data on internal parasites recovered from horses in t w o fields (No. 4 and For P. equorum, mature and No. 10) on a farm in central Kentucky by age of the animals. :i:i:!:!:i:i:i:.:i:i:i:i:!:!:!:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::i:i:i:i:i:i:i:!:i:i:i:i:i:i:i:i:i:i:i:i:i:i:i:!:i:i:i:i:i:i:i:i:i:i:!:!:!:i:i:i:i:i:i:i: immature, the highest prevalence and AMN were in 3- to 6-month-olds. In the 1985 publication 7 for P. equorum, the highest prevalence was in 9- to 12month-olds for both matures and ira!~::!::::!::!!::!::::::!::::::i:::::::::::::::::::::::::::::::::::::::::::::::::::::~::::::::::::::::::::i!~::::::::::::~!::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: matures and AMN was in 3- to 6month-olds for matures and in 9- to 12month-olds for immatures. Oxyuris equi were most prevalent in 6to 9-month-olds and the AMN ~iiiiiiiiii;ii~iii;i!iiiiii;i;ii~i;iii!ii!i!i!iiiiii!~iiii~;;i!i;ii~iiiiiiiiiiiiiiiiiiiiiiiiii~;;i~;;iii;;i;iiiiiiiiiii~ii;~ii;~!~i!!!iiiiiiiiiiiii~;!;!i!~!iiiiiiii was highest in 12- to 18-month-olds. :::::::::::::::::::::: :::::::::::5::::::: :::5::: :: :: :::::::: :::::::::5::: :5::::::::: :5::: :::: :::::::::::::5:::: :::::::::::::::: :::: ::5::::::5 ::5: :::::::: ::::: ::::::5::: :::5:: :::::::::: ::::::::::: :: :::::: i ::::::::::::::::::: ::: 5: :::::::::::::::: :::::::::::: :: :::: :::::: :5:::::::: :: ::::::::::::::::::::: :::::::::: :5: :::::::::::::: This parasite was not present in the Gasterophflus nasa~is horses in the study reported in 1985. 7 2nd instar 3rd instar For the tapeworm, A. perfoliata, Age of highest prevalence was in 9- to 12horses No. No. No. Range AMN month-olds and AMN in 12- to 18(months) exam* inf (%)1- R a n g e AMNtl inf (%) month-olds. For horses in the 1985 re3-6 16 10(63) 1-43 11 4(25) 2-38 13 port, 7 this parasite was most prevalent 6-9 37 4(11 ) 1-36 10 24(65) 1-56 11 in 6- to 12-month-olds and AMN was 9-12 26 1 (4) --1 18(70) 1-34 g highest in 6- to 9-month-olds. 12-18 17 2(12) 6-10 8 14(83) 1-50 10 Thelazia lacrymalis occurred 27 1 0 (0) --0 1(100) --2 All ages 97 17(18) 10 61(63) 10 more commonly and the AMN was SPRING Mar-Apt-May SUMMER Jun-JuI-Aug FALL Sep-Oct-Nov WINTER Dec-Jan-Feb All Seasons

; iiiiiiiiiiiiiiiiiiiiiiiiiii !i i!iii iiiiiiii iiiiii!iiii iiiii i i! i! ! ! ! ! ! !!1 i 11 ii i i ii i ! iU iiiii iU i ! ! !i i i i i !! !!! ! !i iii

iiiiiiiiiii!iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!iii

Continued on next page

104

EQUIN E V E T E R I N A R Y SCIENCE

highest in 6- to 9-month-olds. The prevalence and AMN were highest for this eyeworm in 6- to 9-month-old horses in the 1985 report.7 Prevalence and AMN were highest in 9- to 12-month-olds and 3- to 6month-olds, respectively, for H. muscae. Both of these values were highest forD. megastoma in 12- to 18-montholds. The prevalence and AMN were highest for both species in 6- to 9month-olds for horses in the 1985 publication .7 For the large strongyles in the large intestine, prevalence and AMN were highest for S. vulgaris in 12- to 18- and 9- to 12-month-olds, respectively; for S. edentatus, both values were highest in 12- to 18-month-olds. These parasites were too uncommon in horses in the 1985 paper 7 for comparisons with the present data. Strongylus vulgaris in the cranial mesenteric arteries were more common and the AMN highest in 3- to 9month-olds. In the t985 paper, ~ both prevalence and AMN were highest in 9- to 12-month-old horses. Strongylus edentatus in the ventral abdominal wall were high (94 to 100%) for all age groups and AMN was highest in 9- to 12-month-olds. No other comparable data are available for host age distribution of parenterally located stages of this parasite in horses in Kentucky. Generalizations can be made about the present research. The winter season had the greatest number of species of parasites with the highestrates of infection. The spring and fall months had the highest AMN. Likewise, 12- to 18month-old age groups had the greatest number of species of parasites with the highest prevalences. The 3- to 6- and 12- to 18-month-olds had the highest AMN. This research provides information on transmission and prevalence of natural infections of several species of internal parasites in horses on a farm in central Kentucky over a 19-year-period. Conditions were unique for the research because: (1) the horses were from essentially closed herds, (2) the Volume 10, Number 2, 1990

Table 4 continued Para$cari$ equorum

Mature Age of horses

No. exam*

No. inf(%)

16 37 26 17 1 97

15(94) 30(81 ) 18(70) 9(53) 0 (0) 72(75)

Immature

Range

AMN

No. inf(%)

4-213 1-370 1-214 1-43 ---

58 52 35 16 0 45

8(50) 15(41 ) 7(27) 5(30) 0 (0) 35(36)

Range

AMN

2-149 1-250 1-55 2-7 ---

39 38 15 4 0 29

(months) 3-6 6-9 9-12 12-18 27 All ages

~i~!~i~i~i~i~i~i~i~i~i~i~i~i~i~i~i~i~i~i~i~i ~i~i~i~i~i ~i~i i i i ~i~i~i~i~i~i~i~i~i~i~i~i~i~i~i ~!ii i i !i~i i i i i i ~i~i~i~!ii i~i i i ~i i i ~i~i~i i ~i!i i~i i!i i ~i i i~i~i ~i i i~i i~i ~i i i i~i~i~i~ i i i iiiii~i i ii i iiiiii~il ~!!!~ii!~!!~i~!iiii!i!!ii!i!!!i!!i~i~!~!~i~!~i~i~U:::::!!!:!::i!:i:i:i::!i:::::::::::::::::::::::::::::::: :~ i i ill!if!! !! !i i ii i i i i i ! ! ! ! ! ! ! i i!i!!ii!iiiili!i!i!i!i!i!!ili!!!i!i!i!i!i!iiiiii:i:i:i:i i !~!!! !!iii !ii~iii~ i~!!~!

~iiii~iiiiii~iiiiiiiiiiiiiiiiiiiiii~iiiiiiii~i~iiiiiii~iiii!iiiiiiiiiiii~iiiiii~iii~iiiiiiiiiiiiiiiiii::i::i::i::i::i::i::i~i::i::i~i::i::i::i::i::~::i::i::i~:~i::i::i~i~i~i~i::iii~i:~iii~iiiiiiiiiiiiiiiiiiiiii~iiiiiiii Oxyuris equi Mature Age of horses

No. exam*

No. inf(%)

16 37 26 17 1 97

2(13) 19(52) 13(50) 7(42) 0 (0) 41 (43)

Range

AMN

2-22 1-458 1-238 2-758 ---

12 102 41 149 0 87

{months) 3-6 6-9 9-12 12-18 27 All ages

i~i~i~i~i~i~i~iiiii~i~i~i~i~i!iiii~i~i~!~iiiiiiiiiiiiii~i~!i!iiiiiii!iiiiiii~i~i~i~i~i~i~i~i~!iiii~iii~iii~iiiiiiiiiiiiiiiiii~i~iiiii~iiiiiiiiiii~i~iii~iiiiiiiiiiiii~ii~iiiiiiiiiiiiii~i~i~i~!~iiiiiiiiiiiiiiill~i~ii~iiii iiiiiii~iiiiiiiiiiii~iii~iii!iii~iiiiiii~iiiiiiiiiiiiiiiiiiiiii!ii~i~iiiiiiiiiiiiiiiiiii~iii~~!~!!~i~ii~iiii~i~i!i!iii~i~iiiiii!!i!i!iii!i!~!~i~iiiiiiii!~i~!~i~i~ii~iiiiii~iiiii!i!~!!!!!!!~!!ii~i~iiiiii~i~i~!~!!~!!ii~!ii

i i ii i! i iiiiiiiiii!iiiiiiiiiiii ii i iiiii iiiiiiiii iiiii ii i iii iiiiiiiii i iii iiiiiiiiiiii i i i iiiii i!iiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiii i i i i ii iiiiiiiiiiii i i iiiiiiiiiiiiii i i ii !i ! i ! i ii iii ! i i ii iiii!ii iiiiiiiiiiiii i i ! !iiiiii! i i!ii!iiiiiii i!i!iiiiii i iiii!i!!!i!iiiiiiiiiii ! iiiiiiiiiiii!i!iiiiiiiiii iiiiiiiiiiiiiiiii i iiiiiiiii iii iii iiiiii!! iiii iiiiii!! ! ! i ! ii iiiiiiiiiiiiiiiii!iiii! ! iiiiiiii!!! ii !! iiiiii!ii!! iiiiiiiiiiii iiii!iii i ~i~

i

~iii i!~~ii il iii i~iiii!i iii ~i~i iiiill i i i i~i~i~i!!ii i i i i i i i i i~i~i~iiiiiiiiiiiiiiiiiiii!iiiiiii~i~i~i!iiiiiiiiiiiiiii~i~i~i~i~ii~iiiiiiiiii il

~ii~i~i~!!~!!!i!~ii~i~i!~iiii~iiiiii~iii~i~i~iiiiiiiii!~i!!~i~i~i~i~i~iiiiii~i!i~!~i~!!ii!!iiiiiii~i~i~ii~iiiiiiiii~i~ii~iii~!ii!i~i~i~i~i~ii!!!iii!ii!~!~i~i~iiiiiii~i~i~i~i~iii~!!iii!iii~i~iiiiiiiiii

Continued on next page 105

Table

4

horses had received no antiparasitic drugs before the drug efficacy tests were initiated, and (3) there was very limited usage of these compounds in the other herd animals, Therefore, the findings reflect the natural transmission and prevalence of the parasites studied.

continued Habronema muscae

Age of

No,

No.

horses (months)

exam*

inr(°/o)

Range

3-6 6-9 9-12 12-18 27 All ages

3 31 17 11

2(67) 24(78) 14(83) 6(55) 0 (0) 46(73)

3-408 208 1-290 25 1-444 101 117-443 195 --0 78

i

63

iiii!i

i !ii!

AMN

REFERENCES

i

!i

i

1. Drudge JH, Szanto J, Wyant ZN, Elam G: Critical tests of thiabendazole as an anthelmintic in the horse. Am J Vet Res 24:1217-1222,1963. 2. Drudge JH, Lyons ET, Wyant ZN, Tolliver SC: Occurrence of second and third instars of Gasterophilus intestinalis and Gasterophilus nasalis in stomachs of horses in Kentucky. Am J Vet Res 36:15851588,1975. Continued on next page

iiiii i iiiiiiiiiiiiiiiiii}iiiii iiiiiiiiiiiiiiiiiiiiiiiiiiii i i iiiiiiiiiiiiii}iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii}i i i}iiiiiiiiiiii}ii}}iiiii i}iiiiiiiiiiiiiii Large Intestine

Strongylus vulgaris~

Strongylus edentatus~

Age of horses (months)

No,

No,

No,

No.

exam*

inf(%)-i-

Range

AMNII-

Exam*

inf(%)

3-6 6-9 9-12 12-18 27 All ages

5 37 26 17 1 86

3 (60) 36 (98) 24 (93) 17(100) 1(100) 81 (95)

14-36 1-247 1-653 1-703

27 66 111 82 1 80

0 0 12 17 1 30

. . . . . . . . . . . . . . . . . . 11(92) 1-114 16(95) 2-238 1(100) --28(94)

Range

AMN

23 43 7 34

:i:i:iii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii ii iiii iiiiiiiiiiiiiiiiiiiiiiiiiiii ii iiiiiiiiiiiiiiiiiiiiiiiiiii iiiiiiiiiiiii iiiiiiii iiiiiii~::~::!!i!~!~i!!~!!i!!i~i~!~!iii~!iiiiiiiiiiiiiiiiiiii~i~ii~::i~!!~!~!iiiii::iiii!!i!;iiiii !;iiiiii!ii::iii~iil;::!i!!;i;!;! ~i!;!iiiiiiiiiiiiii~i~i!i~i!!;!;!;i;!i!iiiiiiiiiiiiii::~iiiiiiiii~iiiiiii;iii;i~i ~!i!i!i!iiiiiiiiii~i~!;;~i;~!;~;!!!~i~!!!iiii~i~;;;;;!;;;;;!?i;i;;iii;i~i~i~!~iiii~iii~i~i;;~;;;!!!;i!i!iiiiiiii~;!;;;i!iii?ii;i

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::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::~i :::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: i ::i::i::i i::iiiiii::iiiiiiiiii:i i::iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii ~!iiiiiiiii~iii~iiiiiiiiiiii~i~i~!~iiii!iiiiiiiiii~iiiii~i~iiii~!~!~!~ii~i~! iili~iiiiiiiiii~i~iiiiiiiiii~!~!~i!i~!iiiii!~i~i~i~iiiiiiiiiiii~i~i iiiiiiiiiiiiiiiiiiiililiiiiii~iii::i::i::i~iiiiiiiiiiiii ii~ili::i::i i::iiiiii~i~i::i::iiiil

~iiiiiiii!!i!ii~ii i!!ii~i~i~!i~i i~i i i i~i~i i~i i~i i;!;;~;;~ii i i~~i~;i;~iiiiiii i i i~i~i~!!;!~;~i~i!iii~!!ilillil;!ii li!i!iiiiiili ;; ii~i i i i iiiiiiiiiiiiiiiii;i;iliiiiiiiiiiiii;11iiiiiiiiiiiiiii i i i!i!iiiiiiiiiiil;iiiiiiiiiiiiii;i !i iiiiiiiiiiiiiiiiiiiiiii!iil iiiiiiiiii!iiii~zi;

~iii~iii::i::!:i::iiiii::iii::iiiiiii::i::iii i:iii;::i::i!i!i~iiiii:~i i::i:~i~i~i:;ii::i::i!;iii~i::;::i~iii;i:i~iii~il iiiiiiil;iliiii!iiiiiiiiiiii~ i :::~::::::::::::::::::::::::::::::::::::::::::::::::::::::::: i::;;i!ii~iii::ii~i::iiiiiiiiiiiiiiiiiiiiiiiiiii!iiiii;i?=:~:~

iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!iiiiiiiiiii

Continued on next page

106

EQUINE VETERINARY SCIENCE

3. Lyons ET, Drudge JH: Occurrence of

the eyeworm Thelazia/acrymalis in horses in Kentucky. JParasito161:1122-1124,1975.

Table

4 continued

4. Lyons ET, Drudge JH, Tolliver SC: Thelazia lacrymalis in horses in Kentucky and observations on the face fly (Musca autumnalis) as a probable intermediate host. J Parasitol 62:877-880,1976. 5. Lyons ET, Drudge JH, Swerczek TW, Crowe MW, TolliverSC: Prevalence of Strongy/us vu/garis and Parascaris equorum in Kentucky Thoroughbreds at necropsy. J Am Vet Med Assoc 179:818-819,1981. 6. Lyons ET, Tolliver SC, Drudge JH, Swerczek TW, Crowe MW: Parasites in Kentucky Thoroughbreds at necropsy: emphasis on stomach worms and tapeworms. Am J Vet Res 44:839-844,1983. 7. Lyons ET, Tolliver SC, Drudge JH, Swerczek TW, Crowe MW: Prevalence of some internal parasites recovered at necropsy of Thoroughbreds born in 1982 in Kentucky. Am J Vet Res 46:67g-683,1985. 8. Lyons ET, Tolliver SC, Drudge JH, Swerczek TW, Crowe MW: Eyeworms (The/azia /acryma/is) in 1- to 4-year-old Thoroughbreds at necropsy in Kentucky (1984-1985). Am J Vet Res 47:315• 316,1986. 9. Tolliver SC, Lyons ET, Drudge JH: Prevalence of internal parasites in horses in critical testsof activityof parasiticides over a 28-year-period (1956-1983) in Kentucky. Vet Parasitol 23:273-284,1987.

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FLAVORED ANTACID FORMULA Research has shown that 52% o f 100 apparently clinically normal horses had stomach ulcers when randomly examined endoscopically. This m a y indicate a higher incidence o f ulcers than previously realized. Antacids have been used successfully in the treatment o f stomach ulcers in the horse. Antacid F o r m u l a is a palatable, grandular, apple spice flavored product, convenient as top-dressing, for horses of any age.

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Volume 10, Number 2, 1990

107