Koch’s postulate in reproduction of broiler coccidiosis by co-infection with eight most common Eimeria spp.: a model for future evaluation of new biologics

By:Danielle B. Ayyash

Establish a model of Koch’s postulate for reproducing coccidiosis in broilers

Using this model in future evaluation of new controlling biologics

Purpose:

Groups ofBroilers

Number of Broilers Broiler age atChallenge (d)

Broiler age atSacrification (d)

Challenged

1 10 14 20

2 10 21 27

3 10 28 34

4 10 35 41

Control

1 10 _ 20

2 10 _ 27

3 10 _ 34

4 10 _ 41

Table 1. Description of the different treatments of broilers

Experimental Design :

The esophageal Eimeria-challenge was with a total of 1.76x105 oocysts/bird

Eimeria inocula

E. acervulina, E. mivati, E. maxima, E. necatrix, E. hagani, E. praecox, E. tenella, and E. brunetti

Evaluation of the Koch’s postulate during the 6 days incubation period following an Eimeria challenge at assigned dates of 14, 21, 28 & 35 d of age

Protocols for Anti-coccidial Susceptibility Testing (AST)

1. The mean percent of weight increase

2. The mean feed conversion ratio

3. The mean percent mortality,

Materials and Methods

Materials and Methods

The scoring of the lesions was accomplished by a trained researcher, scoring “0” ‘1’, ‘2’, and ‘3’ (-ve, mild , moderate, severe )

4. The mean score of lesions

5. The mean oocyst counts per gram of intestine- 1cm of 4 different parts of intestine was rinsed in a saline solution to remove fecal material- Weighed- homogenized and put in a 35% NaCl solution for the floatation of oocytes. - floated oocytes were counted in a McMaster chamber

Group1 of broilers

Age at assigned challenge (days)

Percentage of weight increase at 6 days period following each assigned challengeControls Challenged SEM2

1 14 96.3 88.2

10.0

2 21 69.0 54.53 28 41.2 31.74 35 28.8 20.2Mean 58.8a 48.6a

Table 2. Percentage of weight increase in the four control and the four Eimeria-challenged groups after 6 days of assigned challenges

1Each of the four control and four challenged groups had 10 birds2SEM is Standard Error of MeansaMeans in a row followed by the same alphabet superscript are not significantly different (P>0.05)

Results & Discussion

Table 3. Feed conversion in the four control and the four Eimeria-challenged groups at 6 days-incubation period following the assigned challenges

Group1 of broilers

Age at assigned challenge (days)

Feed conversion during 6 days following challenge

Controls Challenged SEM2

1 14 1.1 3.0

0.3

2 21 1.7 3.3

3 28 2.1 2.5

4 35 2.1 3.7

Mean 1.7a 3.1b

1Each of the four control and four challenged groups had 10 birds2SEM is Standard Error of Meansa,bMeans in a row followed by different alphabet superscripts are significantly different (P<0.05)

Table 4. Frequency of mortality in the four control and the four Eimeria-challenged groups at 6 days period following the assigned challengesGroup1of broilers

Age at assigned challenge (days)

Frequency of mortality (%) in controls and Eimeria-challenged birds at 6 days period following the assigned challengesControls Challenged SEM2

1 14 1 (10%)a 4 (40%)a

0.5

2 21 1 (10%)a 2 (20%)a

3 28 0 (0%)a 0 (0%)a

4 35 0 (0%)a 0 (0%)a

Mean 0.5 (5%)a 1.5 (15%)a1Each of the four control and the four Eimeria challenged groups had 10 birds. 2SEM is Standard Error of MeansaFrequencies in a row followed by the same superscript are not significantly different (P>0.05)

Table 5. Mean score of lesions in different parts of the intestine in the four control and the four Eimeria-challenged groups at the end of the 6 days-incubation period following the assigned challenges Group1of broilers

Age at assigned challenge (days)

Intestinal part Mean score of lesions at 6 days period following each challengeControls Challenged SEM2

1 14 DuodenumJejunumIleumCecum

0.0a

0.0a

0.0a

0.0a

1.5b

1.1b

1.6b

1.1b

0.250.180.250.21

2 21 DuodenumJejunumIleumCecum

0.2a

0.0a

0.1a

0.2a

2.0b

1.7b

1.6b

1.6b

0.270.250.260.25

3 28 DuodenumJejunumIleumCecum

0.6a

0.3a

0.0a

0.0a

1.4a

1.6b

0.6b

0.9b

0.250.250.150.22

4 35 DuodenumJejunumIleumCecum

0.25a

0.0a

0.0a

0.0a

0.5a

0.38a

0.38a

0.13a

0.180.140.140.06

Group of broilers

Age at assigned challenge (days)

Intestine part

Mean oocyst count per gram of intestinal organ at end of 6 days period following the assigned challengesControls Challenged SEM

1 14 DuodenumJejunumIleumCecum

0a

0a

0a

0a

42254b

67839b

112843b

96666b

9744161773534226708

2 21 DuodenumJejunumIleumCecum

0a

0a

0a

0a

33715b

36636b

41896b

48041b

858493431017314776

3 28 DuodenumJejunumIleumCecum

0a

0a

0a

0a

6578b

12321b

19029b

7309b

1438307545661978

4 35 DuodenumJejunumIleumCecum

0a

0a

0a

0a

15344a

6506b

2912a

2367a

69561569921756

Table 6. Mean oocysts count per gram of intestinal part in the four control and the four Eimeria-challenged groups at the end of 6 days period

In Conclusion

The Koch’s Postulate for reproducing coccidiosis in broilers, by the 8 most common Eimeria spp

Allow for future development of new immuno-modulators and coccidiostats

- Significant statistical differences in most measured parameters between controls and challenged birds

- A trend of reduction in weight gain and in augmentation of mortality in challenged birds compared to controls.

Thank you for your

Attention !