Pasture populations of cattle nematode larvae in guadeloupe (French West Indies)

International Jouma~for Poraszkhgy Prmted zn Great Britain

Vol. 19, No. 5,pp.

002&7519/89 $3.00 + 0.00 MaxwellPergamon Macr?vllan p/c Q 1989 Australian Society/or Pamsirology

547-554, 1989

PASTURE POPULATIONS OF CATTLE NEMATODE LARVAE IN GUADELOUPE (FRENCH WEST INDIES) G. AWONT,* * Centre

de Recherche

G. COULAUD,~

des Antilles-Guyane,

A. GRUDE~

and L. GRUNER~

Station

de Zootechnie, B.P. 1232, 97184 Pointe a Pitre Cidex, French West Indies t CRVZ de Theix, Laboratoire de la Production de Viande, 63 122 Ceyrat, France $ Centre de Recherche des Antilles-Guyane, B.P. Bl3,97306 Cayenne Cedex, Guyane FranGaise 0 Station de Pathologie Aviaire et de Parasitologie, Nouzilly, 37380 Monnaie, France

Guadeloupe,

(Received 30 October 1987; accepted 13 February 1989) Abstract-AuMoNr G., COULAUD G., CRUDE A. and GRUNER L. 1989. Pasture populations of cattle nematode larvae in Guadeloupe (French West Indies). International Journalfor Parasitology 19: 547-554. The development of numbers of third-stage (L3) larvae of gastrointestinal nematodes after pat (faeces) deposition by heifers is described, using a mathematical model, for seven experiments carried out in Guadeloupe (French West Indies). A dramatic rise in L3 population size occurred on herbage near pats, 1725 days after pat deposition. There was no clear relationship between climatic data and L3 population dynamics. However, 5 successive days of rainfall induced the resumption of larval migration in two experiments. Changing the unit of expression of L3 population size (100 L3 mm2 vs 1000 L3 per kg DM) did not alter estimates of the model parameters. The evolution of L3 population of Haemonchus and Cooperia were similar. INDEX

KEY WORDS:

Bovine nematodes;

Cooperia; Haemonchus; ecology; tropics; model.

INTRODUCTION IN spite

collected between 9.00 and 11 .OO a.m., once or twice each week for 3 months. Each sample consisted of 400 herbage pinches taken around each pat within a radius of0.05 m. The weight of herbage samples ranged between 1SO and 250 g of fresh matter. Dry matter (DM) availability in paddocks, expressed as kg DM m-*, was determined each week on grass collected from 2 x 1 m* quadrats, dried at IOO’C for 24 hand then weighed. Rainfall and total hours of sunlight (MJ day-‘) were recorded daily near the paddocks. Faecal egg counts (F.E.C.) were determined according to Raynaud’s method (1970). Extraction of infective larvae (L3) from grass samples, and subsequent estimation of their numbers, was carried out as described by Gruner & Raynaud (1980). Nonlinear regression was used to adjust and describe the changes in the numbers of L3 on herbage as follows:

of cattle production in Guadeloupe (French West Indies), there are no published data on bovine helminth parasitism with Intensive treatment this country. ~nzimidazole anthelmintics has contributed to the selection of resistant strains of parasites of sheep and goats in the French West Indies (Gruner, Kerboeuf, Beaumont & Hubert, 1986). Pasture management techniques should be employed to reduce anthelmintic treatment and thus the risk of extending resistance to cattle nematodes. Therefore, a detailed understanding of the dynamics of bovine trichostrongyle infective larvae (L3) populations on herbage is required before such pasture management procedures can be recommended with confidence. of the

considerable

development

S(t)

= M G

(t) D(t)

(1)

where t is the time in days from pat deposition to date of sampling, S (t) is a function describing changes in the L3 population (expressed in L3 1000 per kg DM or L3 100 mm*), M is the potential maximal population size which could be expected from hatching, development and migration of L3 from pats [in units of S (r)], G (r) represents the increase and D(t) the decrease in larval number on herbage, as respectively described in the Nelder model (1961) and in the Weibull equation (Dell, Robertson & Haverty, 1983):

MATERIALS AND METHODS Studies were carried out in 1982 and 1983 in the eastern part of Guadeloupe. Pangola pasture (Digitaria decumbens) and natural pasture of Dicanthium caricosum were used in the seven experiments. The climate of this area is characterized by an annual rainfall of 1280 mm and a marked dry season (December-June, 67 mm month-‘). There is little variation in minimum temperature (21-25°C) and maximum temperature (27-32°C). Relative humidity is higher than 70% over the entire year. Creole heifers were put into paddocks of parasite-free pasture for 12-24 h in order to deposit 106148 pats per 1000 m*. Faecal samples were collected for helminth egg counts. Herbage samples were

G(t)

= [l + n exp. (a- b)/b]‘-‘l”’ D (t) = exp. ( - p t*)

(2) (3)

M, a, b, n and p are the adjusted parameters to non-linear regression. The equation and its derived function enabled the 547

548

G. AUMONT, G. COULAUD, A. GRUDE and L. GRUNER

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FIG. 1. Evolution of L3 population on herbage collected near pats after pat deposition in Guadeloupe. Curve adjusted to experimental points (V). The symbol (7) indicates a climatic event taken into account in the model and which has induced resumption of larval activity.

Ecology

of cattle nematodes

characteristics of the dynamics to be computed. These characteristics were, for the period of increasing L3 number: the average slope, the observed maximum slope and its timing, the theoretical maximum slope (TMS) and the maximum population size. For the period when L3 numbers were decreasing they were: the observed maximum slope and its timing, the time to reach 10% of the population size. For the whole period, the area below the curve adjusted to the experimental points was calculated. TMS was computed from the following equation (Debouche, 1979): TMS = (M/b)(l+n).-(“+“‘”

(4)

One climatic event in experiment 3 and two in experiment 7 induced resumption of larval activity. For these cases, two or three models similar to that described above (1) were associated: S(t) where S (t) is the and Sl (1) are the after the climatic survival duration passed from pat

= So (I) + Sl (t - el)

(5)

evolution of the L3 population models of the L3 population size event that occurred at time el. of L3 was considered to be equal deposition to the data of three

size, So (I) before and Maximum to the time successive

549

error of the model parameters and the data of the L3 population dynamics are given in Tables 1,2 and 3 for total populations (L3 unit per kg DM or per m*) and for these two genera (L3 unit m-*). There was a dramatic increase in L3 population size on pasture, 18-25 days after pat deposition (Fig. 1: experiments 1,2,4,5 and 6). A second peak of L3 was observed 19-21 days after the start of climatic events (defined as 5 successive days of rainfall) in experiments 3 and 7, respectively, and a third one 11 days after the start of a similar event in experiment 7. The herbage dry matter varied between 0.086 and 0.708 kg m-* (Fig. 2). The variance accounted for by the models ranged between 90.2 and 99.0% of the total variance (Table 2). The larvae first appeared on grass 5-10 days after pat deposition. The maximum survival of larvae varied between 63 and 105 days (Table 3). There was no significant correlation between the L3 population evolution (Tables 2 and 3) and climate (Table 4). Changing the L3 units (100 L3 m-* vs 1000 L3 per kg DM) did not significantly affect the parameters of the model, i.e. a, b, n, ,U (Table 1). However, the

TABLE I-ESTIMATESOFTHE PARAMETERS AND STANDARDERRORSOFTHEMODELORTAINEDBYFITTINGEQUATIONS (l)-(4) (EXPERIMENTS 1,2,4, 5, 6) AND EQUATIONS(l)-(5) (EXPERIMENTS 3, 7) TOOBSERVEDNUMBERSOF L3 ON PASTURE.USINGNON-LINEARREGRESSION

Experiment

M (L3 unit)

SEM.

a

S.E.M

(days)

Total third-stage larvae population 153 3.4 15.1 1921 60.1 10.3 148 4.7 17.0 238 4.3 19.8 158 3.1 11.8 775 5.3 16.8 Total third-stage larvae population 388 17.8 17.0 1547 99.3 10.2 319 9.7 17.3 874 25.7 19.7 506 7.2 12.2 2713 18.7 16.8

RESULTS

frequently

encountered.

S.E.M

n

size expressed as L3 x 1000 per kg DM 0.3 0.0052 I .2 4.2 0.3 0.000 1 2.2 2.0 0.1 1.1700 1.1 1.2 0.3 0.7000 0.6 3.6 0.0 0.0000 1.0 1.5 0.2 0.1106 1.3 2.7 size expressed as L3 x 100 mm2 0.6 0.0001 1.o 5.5 0.3 0.6800 1.2 2.5 0.0 1.2000 1.2 1.2 0.4 0.1136 0.0 3.4 0.0 0.0004 0.5 1.6 0.2 0.1107 1.1 2.7

samples free of larvae. The Spearman correlation test (Siegel, 1956) was used to estimate the relationship between the different characteristics of L3 population evolution and climatic data (rainfall in mm day-‘, mm 4 days-‘, mm 7 days ‘, global radiation). The effect of the L3 unit (per m2 or per kg DM) and of the different genera (Haemonchus or Cooperia) on the characteristics of L3 population evolution was tested with the Wilcoxon test (Siegel, 1956). The chisquare test was used to analyse the evolution of the contribution of different genera to the L3 populations at different peaks of population size in experiments 3 and 7.

Haemonchus, Mecistocirrus, Cooperia and Oesophagostomum Cooperia and Haemonchus being

b (days)

Trichostrongylus,

were found, the genera most The estimates and standard

SEM

P

S.E M

0.0006 0.0000 1.1214 0.0957 0.0000 0.0067

0.0011 0.0023 0.0025 0.0015 0.0036 0.0045

0.0001 0.0001 0.0001 0.0002 0.0002 0.0001

0.0000 0.1600 0.1370 0.0126 0.0000 0.0043

0.0011 0.0009 0.0024 0.0014 0.0030 0.0048

0.0001 0.000 1 0.0001 0.0001 0.0001 0.0004

appearance of maximum size was delayed by 1 day and the ratio of observed to theoretical maximum growing slope was increased (+ 0.041; P < 0.005). The ranking of maximum size of the L3 population between the experiments was altered by the change in L3 units (Table 2). The dynamics of L3 populations of Haemonchus and Cooperia genera were similar. However, in experiment 3, the frequency with which Cooperia larvae were observed increased (P < 0.01) from the first to the second peak (43.3 vs 58.4%). Over the same period, the frequency with which Haemonchus larvae were observed decreased (28.0 vs 17.0%; P < 0.01). In experiment 7, a similar significant change (P < 0.01) was recorded from the first to the third L3 peak (Cooperia: 36.7, 54.6, 58.9%; Haemonchus: 41 .l, 29.8, 23.3%).

550 TABLE

G. AUMONT, G. COULAUD, A. 2
L3

GRUDE

and L.

GRUNER

POPULATIONOFBOVINEHFLMINTHSONPASTUREINGUADELOUPEDUR~NGTHEGROW~NCANDTHE MAXIMUMSTAGEOFTHEPOPULATIONSIZE

Explained variance

Experiment

Growing

W) Total third-stage

I 2 3 4 5 6 Mean S.D Total third-stage

1 2 3 4 5 6 Mean S.D Haemonchus

size expressed 4.62 7.10 5.17 4.19 6.86 5.33

as L3 1000 per kg DM 0.500 0.735 0.313 0.429 0.546 0.287

95.9 2.1 larvae population 97.4 90.2 94.8 90.2 98.7 96.6

5.55 1.19 size expressed 4.32 6.08 5.07 4.06 6.55 5.37

0.468 0.165 as L3 100 mm2 0.594 0.843 0.401 0.510 0.581 0.196

third-stage

2 3 4 5 6 Mean C’o?peri~ third-stage 2 3 4 5 6

Maximum

OMS/TMS

larvae population 97.8 94.3 92.4 96.7 96.7 97.3

1

1

stage

Av. slope W)

94.7 3.7 larvae population 94.3 92.0 94.6 96.3 97.2 97.8

5.24 0.97 size expressed 4.00 6.81 5.00 3.97 6.72 5.41

95.4

5.32

larvae2.2 population 97.3 92.7 94.6 95.4 99.00 96.4

Mean

95.9 2.2

SD.

size1.25 expressed 4.37 4.21 4.94 4.43 6.65 5.37 5.00 0.92

0.521 0.216 as L3 100 mm’ 0.689 0.258 0.299 0.548 0.529 0.185 0.418

size stage (peak)

Time (days)

Max. size (L3 unit)

OM/TM

21.6 14.1 19.4 24.0 14.6 18.8

76 1070 51 76 63 100

0.494 0.557 0.344 0.318 0.398 0.129 0.373 0.150

18.7 3.9 23.3 16.5 19.7 24.7 15.3 18.6

141 I108 111 306 217 312

19.7 3.7 25.0 14.7 20.1 25.3 14.9 18.5

0.387 0.194 66 445 43 69 46 64

17.8 23.7 20.2 22.6 15.0 18.6

0.466 0.244

19.7 3.2

0.475 0.718 0.263 0.357 0.462 0.104 0.397 0.209

19.8 4.7

as L3 0.198 100 mm” 0.786 0.587 0.157 0.482 0.583 0.198

0.363 0.716 0.348 0.350 0.429 0.115

49 407 43 224 157 183

0.575 0.668 0.379 0.350 0.426 0.114 0.419 0.193

The slopes are expressed in per cent of maximum per day. OMS, Observed maximum slope. TMS, Theoretical maximum slope (Nelder, 1961; Debouche, 1979). OM, Observed maximum size (Nelder, 1961; Debouche, 1979). TM, Theoretical maximum size.

DISCUSSION The genus structure

of our helminth population is similar to those reported for tropical Latin-American areas (Melo & Gomes, 1979; Catto, 1981; Catto & Ueno, 1981; GirBo, GirHo & Medeiros, 1985; Esterre & Maitre, 1985). In these tropical areas such studies have generally involved a restricted number of artificial pats (Tongson & Tong, 1973; Catto, 1982; Delgado, 1982, 1983a,b). In contrast, our experimental design was more representative of natural pasture contamination. Pats were deposited in high numbers to minimize the variations between pats.

Great attention was paid to the removal of all remaining pats from the paddocks before the start of the experiment and to the identification of each pat to avoid sampling errors. The residual variations within an experiment in our model were low. The variations between experiments of environmental conditions, such as climate and herbage dry matter, were generally high (Table 4, Fig. 2). Thus comparisons of different experiments needed a precise model for the adjustment of experimental data. The use of the non-linear function suggested some biological hypothesis: the amount of L3 migrating

Ecology TABLE

3--CHARACTERISTICS

OF

L3

POPULATION

AREA BELOW ADJUSTED

OF BOVINE HELMINTHS CURVE AND MAXIMAL

Maximum decrease stage

Experiment

Time (days)

ON PASTURE IN GUADELOUPE SURVIVAL

10% maximum stage Time (days)

Slope (% days)

Time after peak (days)

larvae population 30.5 19.3 22.6 30.8 18.0 22.5 -

size expressed 4.41 6.35 8.46 5.76 9.16 11.18

as L3 1000 per kg DM 52.3 30.7 53.4 21.4 36.7 17.3 47.9 24.0 29.9 15.4 31.1 12.3

Mean

24.0 5.5 larvae population 31.8 25.5 23.0 31.3 19.1 22.3 -

7.55 2.49 size expressed 4.87 3.56 8.28 5.52 8.18 11.70 -

41.9 10.6 as L3 100 mm* 50.9 52.0 37.4 49.8 32.4 30.5

S.D.

Mean s D. Haemonchus 1 2 3 4 5 6 7 Mean C$mia

25.5 7.01 5.1 2.96 third-stage larvae population 34.1 4.32 20.8 4.26 22.7 10.36 32.9 5.04 18.2 8.24 22.0 12.07 -

third-stage

DURATION

(M.S.D.)

M.S.D. (+ days)

95.0 104.0 105.0 74.0 78.0 63.0 98.0

27.7 26.5 17.7 25.2 17.1 11.9

42.3 21.1 10.1 6.4 size expressed as L3 100 me2 56.0 31.0 45.0 30.3 34.8 14.8 52.5 27.3 32.0 17.1 29.9 11.4

25.1 7.34 41.7 22.0 larvae 6.7 population 3.31size expressed 11.1 as L3 100 m-* 8.6

STAGE,

Area below adjusted curve 1 peak (L3 unit days) 1763 16,213 634 1563 669 1030 1202

323 1 28,929 1390 5841 2583 3138 311

All peaks

3355

4822

7789 1722 -

77.0 104.0 105.0 74.0 78.0 63.0 76.0

2833 16,373 454 1450 514 627

3.48 2.63 7.59 6.73 8.13 12.00 -

52.9 73.6 39.5 43.8 32.4 30.2

30.0 49.9 19.2 21.2 17.4 11.6

95.0 104.0 105.0 74.0 78.0 63.0 98.0

Mean

27.2 7.1

6.76 3.40

45.4 16.1

24.8 13.6

88.1 16.4

1568 -

73.9 34.1

33.5 31.7 23.7 27.1 19.2 22.1 -

Slopes are expressed

THE DECREASING

L3

20.2 6.6

1 2 3 4 5 6 7

S.D.

DURING OF

size

Total third-stage 1 2 3 4 5 6 7

Total third-stage 1 2 3 4 5 6 7

551

of cattle nematodes

1407 7629 589 3270 1899 1760

4360 -

in % of maximum size per day.

from pats to herbage must be limited and poorly dependent on environmental events; the increase in the L3 population size was not constant and the maximum size depended on interaction between the migration rate and mortality (or disappearance) rate. This model is a simple deterministic representation of complex population processes. Many more samples are necessary, especially during the first month after pat deposition (three or four samples per week) if a more precise model is to be used with a two-compartment scheme: pats and herbage compartments, each with a specific mortality rate function as defined in formula

4, and variable passage rate from pat to herbage compartment as defined by the Nelder equation (Nelder, 1961). Nevertheless, the close correlation between computed and experimental data confirms our hypothesis. In a tropical climate, temperature and moisture within pats during the 2 weeks following deposition are optimal for egg hatching and larval development. This was indicated by the appearance of L3 on herbage around the pats, 5-10 days after deposition and the high average growth rate of the L3 population (4.06 7.10% day-‘). The observed maximum slope and size

552

G.AUMONT,G.COULAUD,A.

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FIG. 2. Variations

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paddocks.

553

Ecology of cattle nematodes 1,2,3,4,5,6

TABLE~--WEEKLYRA~NFALLANDWEEKLYGLOBALRADIAT~ONRECORDEDDURINGEXPERIMENTS

Experiment Date of pat deposition

2 4 5 6

10.08.82 03.12.82 31.03.83 10.11.82 02.03.83 04.05.83 19.07.82

0

1

2

8.4 4.8 0.0 37.0 33.0 8.0 38.0

39.7 54.5 29.4 82.5 13.0 26.0 32.5

22.2 8.4 69.4 34.0 0.0 105.0 13.0

167 112 171

131 102 155

101 132 126 139

94 135 96 139

Weekly 145 103 145 112 141 99 140

3

4

Weeks after pat deposition 5 6 7 8

Weekly rainfall (mm 19.5 95.3 10.6 171.3 20.0 17.6 0.7 3.3 10.3 2.5 44.0 49.5 9.5 0.0 9.5 11.5 11.0 17.2 14.0 20.5’ 25.0 global 138 63 164 122 152 149 156

week- ‘) 67.3 4.0 0.4 10.6 28.0’ 55.8 118.5 100.5 35.5 0.5 0.9 2.8 48.0 5.0

radiation (MJ me2 week-‘) 136 154 121 134 114 95 118 122 161 136 107 103 99 88 75 84 162 167 145 153 164 118 137 156 137 143 128 156

AND7

9

10

11

12

13

2.1 2.8 3.9 12.5 1.0 10.9 75.5*

56.9 0.0 24.5 9.0 8.0 14.7 30.0

19.1 3.2 0.9 8.0 26.0 3.5 93.5

29.4 0.2 1.6 2.0 98.3 0.8 1.0

12.5 0.0 1.6 0.0 10.5 9.9 2.0

36.8 14.9 15.7 1.5 8.0 24.5 52.0

149 125 160 117 149 167 127

116 129 136 118 126 160 130

129

133 123 164 122 99 120 152

125 150 158 129 149 119 136

107

143 144 111 96 156 109

132 143 139 164 138 106

* Climatic events defined as 5 successive days with rainfall.

of L3 populations are low when compared with theoretical ones (their ratios are low). This indicates that only a small part of the population was observed on grass. The major part was comprised of dead larvae and L3 that migrated from pats and herbage into the soil, as was shown by Delgado (1982,1983a,b) with the same genera in Cuba. Grenfell, Smith At Anderson (1986) showed that a temperature higher than 30°C dramatically increased the mortality rate of third-stage larvae of Ostertagia up to 4.0% day-‘. Delgado (1982, 1983a) recorded a 0.87% increase for Haemonchus and 0.89 for Cooperia (computed from data). The mortality rates recorded in our study (i.e. 4.1% for Haemonchus and 3.6% for Cooperia) between the time of maximum number of L3 and the time at which the population size is 1% are similar to those recorded by the cited authors. The percentage of Cooperia L3 significantly increased in the successive peaks in experiments 3 and 7 indicating a lower susceptibility to mortality factors than Haemonchus L3. The maximum survival duration is difficult to estimate since it depends on the sampling frequency and on the detection limit of the L3 extraction method. In this study, the values extended from 63 to 105 days without any difference between genera. Higher values were recorded by Delgado (1982, 1983a) and Benitez-Usher, Marciel, Reboll & Armour (1984) and lower values were reported by Tongson & Tong (1973) in the Philippines and Valle (1984) in Cuba. Temperature is probably the major cause of L3 mortality on herbage. It appeared that seasonal factors had no consistent effect on the dynamics of L3 populations. The pats constituted a stock of L3 protected from solar radiation. Five successive days of rainfall brought about a resumption of larval activity as noted by Melo (1977), Catto (1982) and Benitez-Usher et al. (1984). The results were quite

different from the caprine trichostrongyle species in the same area in Guadeloupe, where L3 populations were largely dependent on the season (Gruner, Peroux & Aumont, 1984; Aumont & Cruner, 1989). A humid tropical climate is often adequate for grass production. It induces great variation within and between fields in the DM amount per unit area. In this study, the herbage dry matter ranged from 0.086 to 0.708 kg m-*. Changing the L3 units (100 L3 mm2 vs 1000 L3 per kg DM) did not alter the characteristics of the L3 population dynamics within each experiment, except for the ratio of observed to theoretical maximum size and for the time at which the size of the L3 population reached a maximum. In contrast, the ranking of the maximum sizes of larval populations and the areas below adjusted curves were modified between experiments This is important because the L3 population size represents a good estimate of the parasitic infection risk (Aumont, in press). For example, in spite of equal maximum size, the areas under adjusted curves in experiments 4 and 6 were substantially different (5841 100 L3 days mm2 vs 3138 100 L3 days-‘). The area below the adjusted curve of experiment 4 was equal to that of experiment 1 when expressed as 1000 L3 days per kg DM, and twice as high when expressed as 100 L3 days m-*. These two ways of measuring pasture infection are of equal significance for epidemiological considerations. In conclusion, it can be assumed that the first and major event that happens after pat deposition on pasture in Guadeloupe is a striking rise in the L3 population size on herbage, 1625 days after faeces deposition. This phenomenon was not dependent on the season and no relationship was found between climate and population characteristics. Five successive days of rainfall induced the resumption of larval activity. The amount of dry matter available on the

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G. AUMONT, G. COULAUD, A. GRUDEand L. GRUNER

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