Immune Response and Vaccination Efficacy Against Haemonchus Contortus in Goats

Last Updated: January 22, 2026
Estimated reading time: 7 minutes
Word count: 1380

The development of sustainable control strategies for gastrointestinal nematodes relies heavily on understanding the host’s ability to mount a protective defense. In the context of Haemonchus contortus infection, the immune response is the biological battleground where the host attempts to expel or suppress the parasite. This post delves into the pivotal results of the vaccination trials conducted on Indian goat breeds, analyzing the efficacy of Crude Somatic Antigens (CSA) versus Excretory/Secretory (ES) antigens, and characterizing the specific antibody kinetics that define resistance.

Key Takeaways:

• Antigen Efficacy: Both Excretory/Secretory (ES) and Crude Somatic Antigens (CSA) significantly reduced faecal egg counts in vaccinated goats compared to controls.
• Antibody Persistence: The immune response induced by ES antigens was more sustained, maintaining high antibody titers longer than the response triggered by CSA.
• Protein Profile: SDS-PAGE analysis revealed that CSA contains a broader spectrum of polypeptides (17 bands) compared to the more specific ES antigens (9 bands).
• Breed Uniformity: Unlike natural infection, vaccination elicited a similar degree of protection and antibody production in both Jamunapari and Sirohi breeds.
• Reduction Metrics: Vaccination resulted in faecal egg counts that were 3–4 times lower in treated groups compared to infected controls by day 35 post-infection.

RESULTS: VACCINATION AND IMMUNOLOGICAL CHARACTERIZATION

Characterization of Antigens via SDS-PAGE

Before assessing the immune response in live animals, the study first characterized the molecular composition of the vaccines used. Using Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE), the researchers analyzed the protein profiles of the Haemonchus contortus antigens. This step is crucial for identifying which specific viral or parasitic proteins might be responsible for triggering immunity. The analysis showed a clear distinction between the somatic body parts of the worm and the products it secretes.

“CSA showed 17 polypeptides bands of different molecular weight… ES antigen revealed number of proteins with apparent molecular weight between 20 and 95 kDa” (Agrawal, 2009, p. 119).

The Crude Somatic Antigen (CSA) was complex, displaying 17 distinct bands, whereas the Excretory/Secretory (ES) antigen was more refined with 9 visible bands. Major bands in the ES antigen were clustered between 10 and 16 kDa, with a dominant product at 15 kDa. This molecular “fingerprint” suggests that the ES antigen contains specific low-molecular-weight proteins that the parasite releases to interact with the host, potentially making them sharper targets for the immune system compared to the “soup” of proteins found in the whole-worm somatic extract.

Student Note / Exam Tip: In SDS-PAGE, kDa (kilodalton) measures the molecular weight of proteins. Lower kDa bands (like the 15 kDa found here) often correspond to specific surface or secretory proteins that are highly immunogenic.

Professor’s Insight: The finding of a dominant 15 kDa band in the ES antigen is significant; many successful nematode vaccines globally target these “hidden” or secretory gut antigens.

Vaccination Efficacy: Reduction in Faecal Egg Counts

The ultimate test of any immune response is whether it stops the parasite from reproducing. The study divided goats into three groups: Group A (immunized with ES antigen), Group B (immunized with CSA), and Group C (Unimmunized Control). All groups were challenged with 10,000 infective larvae. The results were striking. By day 35 post-infection, the control group showed massive worm burdens, while the vaccinated groups significantly suppressed egg shedding.

“On day 35 PI EPG values in infected control was 3.45 and 3.97 times higher in comparison to group A and group B in Jamunapari breed” (Agrawal, 2009, p. 120).

The data demonstrated that vaccination acts as a potent check on parasite fecundity. While the vaccines did not result in “sterile immunity” (zero worms), they drastically lowered the contamination potential. Specifically, the reduction in egg counts in the ES-vaccinated group (Group A) and CSA-vaccinated group (Group B) was comparable, proving that exposing the goat’s immune system to worm proteins—whether from the gut or the body—primes it to fight off a subsequent heavy challenge.

Student Note / Exam Tip: Sterile immunity (complete prevention of infection) is rare in helminth vaccines; the goal is usually reduction in fecundity (fewer eggs) and worm burden, which reduces pathology and pasture contamination.

Professor’s Insight: Notice that both antigen types worked. This gives vaccine developers flexibility—ES antigens are harder to collect (requires culturing worms), while CSA is easier (just crushing worms), but ES might offer better long-term specificity.

Group	Antigen Type	Jamunapari FEC (Day 35)	Sirohi FEC (Day 35)	Reduction vs Control
Group A	Excretory/Secretory (ES)	8.11 ± 0.51 (Log)	8.41 ± 0.39 (Log)	Significant
Group B	Crude Somatic (CSA)	8.36 ± 0.14 (Log)	8.58 ± 0.51 (Log)	Significant
Group C	Control (None)	9.69 ± 0.17 (Log)	9.12 ± 0.17 (Log)	None

Fig: Comparative efficacy of vaccines showing Mean Log Faecal Egg Counts in infected goats (Reformatted from Tables 18 & 19, p. 126).

Humoral Immune Response: Antibody Kinetics

The study utilized ELISA to track the “humoral” immune response, which specifically refers to the production of antibodies circulating in the blood serum. Monitoring antibody titers over time revealed a distinct difference in how the goat’s immune system reacted to the two different antigen types. While both groups produced antibodies, the persistence of these antibodies varied.

“Only ES immunized goats maintained their antibody levels for longer period” (Agrawal, 2009, p. 120).

In the CSA-immunized group, there was a steep, rapid rise in antibody titers shortly after vaccination, but these levels receded quickly. In contrast, the ES-immunized group showed a more gradual rise but maintained high antibody titers well into the post-infection period. This suggests that the Excretory/Secretory products, being the natural substances released by the worm during feeding and movement, provide a continuous or more “memorable” stimulus to the immune system. For a vaccine to be practical in the field, this longevity (persistence) is just as important as the initial spike.

Student Note / Exam Tip: Humoral immunity involves B-cells and antibodies (immunoglobulins), whereas Cellular immunity involves T-cells and direct cell killing. ELISA primarily measures the Humoral response.

Professor’s Insight: The “steep rise and fall” of the CSA response is typical of somatic antigens—they are foreign but don’t mimic the active infection as well as ES antigens, which sustain the immune memory longer.

Comparative Breed Response to Vaccination

A major question of the thesis was whether the “resistant” Sirohi breed would react differently to vaccination compared to the “susceptible” Jamunapari breed. Under natural infection conditions, Sirohi goats showed significantly lower egg counts and better resistance. However, interestingly, the results of the vaccination trial showed little difference between the breeds.

“In the case of breeds, little variations were observed when goats immunized either with CSA or with ES antigens” (Agrawal, 2009, p. 113).

Both breeds mounted a robust immune response, with sharp rises in antibody titers and significant reductions in egg counts. This indicates that while Sirohi goats have better innate or natural resistance (likely due to genetic traits unrelated to specific antibodies, such as gut physiology or mucus traits), both breeds are equally capable of mounting an acquired immune response when artificially stimulated by a vaccine. This is a positive finding for farmers, as it implies that a potential Haemonchus vaccine would be effective across different breeds, regardless of their natural susceptibility levels.

Student Note / Exam Tip: Distinguish between Innate Resistance (genetic, present before exposure) and Acquired Resistance (developed after exposure or vaccination). This study shows both breeds have similar potential for Acquired Resistance.

Professor’s Insight: This result simplifies breeding and health programs—you don’t need different vaccines for different breeds. The biological machinery to produce antibodies is intact even in the more susceptible Jamunapari.

Real-Life Applications

1. Vaccine Development Strategy: The study proves that ES antigens provide a longer-lasting immune response. Therefore, future commercial vaccines should prioritize isolating these secretory proteins (or recombinant versions of them) rather than just crushing whole worms.
2. Universal Vaccination Protocols: Since both Jamunapari and Sirohi breeds responded equally well to the vaccine, a single vaccination protocol can be rolled out across mixed-breed herds without needing breed-specific adjustments.
3. Monitoring Herd Health: The correlation between antibody titers (ELISA) and reduced egg counts validates the use of serological testing to check if a flock has immunity, rather than waiting for clinical signs of anaemia to appear.
4. Biological Control: By reducing the egg output by nearly 4 times, vaccinated animals act as “biological dead ends” for the parasite, cleaning up the pasture for future grazing cycles.

Why this matters: Moving from chemical dewormers (which parasites resist) to immunological control (vaccines) is the future of sustainable livestock farming. Understanding which antigens work best is the first step in this transition.

Key Takeaways

• Effective Reduction: Vaccination with worm antigens reduced parasite egg output by roughly 75–80% compared to non-vaccinated animals.
• Antigen Superiority: Excretory/Secretory (ES) antigens induced a more persistent antibody response than Crude Somatic Antigens (CSA).
• Molecular Targets: The 15 kDa protein band in ES antigens is a potential candidate for recombinant vaccine engineering.
• Breed Parity: Genetic differences in natural resistance did not affect the ability to respond to vaccination; both breeds benefited equally.
• Serological Diagnostics: ELISA tracking of antibody titers accurately reflected the protection levels, serving as a valid research tool.

MCQs

1. Which antigen type elicited a more sustained antibody response in the experimental goats?
   A. Crude Somatic Antigen (CSA)
   B. Excretory/Secretory (ES) Antigen
   C. Recombinant DNA Antigen
   D. Larval Cuticular Antigen
   Correct: B
   Difficulty: Moderate
   Explanation: The study noted that only ES immunized goats maintained their antibody levels for a longer period compared to the CSA group (Agrawal, 2009, p. 120).
2. How many polypeptide bands were identified in the Crude Somatic Antigen (CSA) using SDS-PAGE?
   A. 5 bands
   B. 9 bands
   C. 17 bands
   D. 25 bands
   Correct: C
   Difficulty: Easy
   Explanation: SDS-PAGE analysis showed that CSA contained 17 polypeptide bands, while ES antigen showed 9 bands (Agrawal, 2009, p. 119).
3. What was the effect of vaccination on Faecal Egg Counts (FEC) in the infected control group vs. vaccinated groups?
   A. No difference
   B. Vaccinated groups had higher FEC
   C. Control group had 3-4 times higher FEC
   D. Control group had lower FEC
   Correct: C
   Difficulty: Moderate
   Explanation: On day 35 post-infection, the infected control group showed EPG values 3.45 to 3.97 times higher than the vaccinated groups (Agrawal, 2009, p. 120).

FAQs

Q: Why do ES antigens work better for long-term immunity?
A: ES antigens are actively secreted by the worm during infection, constantly stimulating the host’s immune system. Somatic antigens are only “seen” by the host when a worm dies and degrades, providing less continuous stimulation.

Q: Did the vaccination completely stop the goats from getting infected?
A: No, it did not prevent infection completely (sterile immunity), but it significantly reduced the severity of the infection and the number of eggs shed into the environment.

Q: Is the immune response different between Jamunapari and Sirohi goats?
A: In terms of vaccination, no. Both breeds produced similar levels of antibodies. However, under natural infection without vaccination, Sirohi goats are more resistant.

Lab / Practical Note

Lab Tip: When performing SDS-PAGE, ensure the “stacking gel” and “separating gel” have the correct pH (6.8 and 8.8 respectively). If the pH is off, the protein bands will not resolve clearly, making it impossible to distinguish between the 17 bands of CSA and the 9 bands of ES.

External Resources

• NCBI: Vaccines against gastrointestinal nematodes
• ScienceDirect: Immune mechanisms in small ruminants

Sources & Citations

Thesis: Comparative Study on Immune Response and Resistance Status in Indian Goat Breeds Against Haemonchus contortus Infection, Ms. Nimisha Agrawal, Supervisor: Dr. D.K. Sharma, Central Institute for Research on Goats (CIRG), Makhdoom, Mathura, 2009. Pages 112, 113, 119, 120, 126.

Disclaimer: This summary was assisted by AI and verified by a human editor. It is intended for educational purposes only.

Author: Ms. Nimisha Agrawal (Ph.D. Candidate), Central Institute for Research on Goats.
Reviewer: Abubakar Siddiq