Immune Response and Resistance to Haemonchus contortus Infection in Goats

Last Updated: January 17, 2026
Estimated reading time: ~6 minutes

Parasitic gastroenteritis remains a significant hurdle in small ruminant production, with Haemonchus contortus infection acting as a primary constraint on goat health and productivity in tropical regions. This dominant nematode species causes severe economic losses through mortality, reduced weight gain, and lowered milk production, particularly in developing countries. Understanding the host-parasite interaction, specifically how different breeds mount immune responses, is crucial for developing sustainable control strategies that reduce reliance on chemical anthelmintics.

This comprehensive study evaluates the epidemiological patterns, genetic resistance, and immunological responses of two indigenous Indian goat breeds—Jamunapari and Sirohi—when challenged by this blood-sucking parasite. By analyzing seasonal trends, hematological shifts, and vaccine efficacy, students and researchers can gain vital insights into managing parasitic burdens in livestock.

• Rainy seasons trigger the highest infection rates due to favorable conditions for larval development.
• Sirohi goats demonstrate higher natural resistance compared to the Jamunapari breed.
• Anemia is a hallmark of infection, evidenced by significant drops in Hemoglobin (Hb) and Packed Cell Volume (PCV).
• Excretory/Secretory (ES) antigens show promise in vaccination trials compared to Crude Somatic Antigens (CSA).
• Faecal Egg Counts (FEC) serve as a reliable indicator for selecting naturally resistant breeding stock.

Comparative Study on Immune Response and Resistance Status in Indian Goat Breeds Against Haemonchus contortus Infection

Epidemiology and Seasonal Prevalence

The epidemiology of gastrointestinal nematodes is heavily influenced by climatic variables, with temperature and humidity playing pivotal roles in the development of free-living larval stages. This study monitored incidence rates over two years (2006–2008) in a semi-arid region, revealing distinct seasonal patterns. The data indicates that environmental moisture is the primary driver for the proliferation of infective larvae on pasture, leading to higher host infection rates during specific months.

“The analysis of season wise grouped data revealed that highest incidence was found during rainy season in both the breeds i.e. 56.34 percent in Jamunapari and 58.50 percent in Sirohi” (Agrawal, 2009, p. 76).

Understanding these seasonal dynamics is essential for timing preventive interventions. The study observed that the “monsoon” period provides the optimal microclimate for the hatching and survival of Haemonchus larvae. Conversely, extreme heat in summer and low temperatures in winter act as natural suppressors of the parasite population. For veterinary students, this highlights the importance of strategic deworming protocols that anticipate these seasonal peaks rather than relying on fixed-interval treatments which may accelerate drug resistance.

Student Note / Exam Tip: The rainy season is the critical epidemiological window for nematode transmission due to high humidity facilitating larval survival.

Season	Jamunapari Incidence (%)	Sirohi Incidence (%)	Relative Intensity
Summer	48.08	31.56	Moderate
Rainy	56.34	58.50	High (Peak)
Winter	25.29	21.55	Low

Fig: Seasonal incidence rates of nematode infection in two goat breeds (Reformatted from Agrawal, 2009, Table 5).

Professor’s Insight: In exam scenarios, always link high rainfall and humidity directly to increased pasture contamination and subsequent peaks in parasitic gastroenteritis.

Genetic Resistance: Jamunapari vs. Sirohi

Genetic resistance to internal parasites varies significantly between breeds, offering a sustainable avenue for disease control through selective breeding. This research compared the susceptibility of Jamunapari and Sirohi goats, two prominent Indian breeds, by measuring Faecal Egg Counts (FEC). The findings suggest that native breeds evolved in harsher, semi-arid environments may develop robust resilience mechanisms, allowing them to maintain productivity despite parasitic burdens.

“The Sirohi does (5.97±0.07 eggs/g) seems to be relatively less susceptible to H. contortus infection than Jamunapari does (6.30±0.05) in different physiological stages” (Agrawal, 2009, p. 91).

The study utilized “Least Square Means” to analyze the log-transformed egg counts, ensuring statistical accuracy. The consistently lower egg counts in the Sirohi breed imply a superior innate ability to limit worm establishment or fecundity. This breed-specific trait is vital for genetic improvement programs. By selecting breeds like the Sirohi for high-risk grazing areas, farmers can naturally reduce pasture contamination. This concept of “host resistance” is becoming increasingly important as anthelmintic resistance renders chemical drugs less effective globally.

Student Note / Exam Tip: Sirohi goats exhibit greater natural resistance to gastrointestinal nematodes compared to Jamunapari goats, indicated by lower FEC.

Breed	Mean LFEC (Adults)	Mean LFEC (Kids)	Resistance Status
Jamunapari	6.01 ± 0.05	5.45 ± 0.05	More Susceptible
Sirohi	5.73 ± 0.06	4.97 ± 0.14	More Resistant

Fig: Comparison of Least Square Means for Faecal Egg Count (LFEC) between breeds (Reformatted from Agrawal, 2009, Tables 6 & 7).

Professor’s Insight: When asked about biological control, remember that exploiting “between-breed variation” is a viable strategy to improve herd immunity without drugs.

Haematological Impact of Infection

Haemonchus contortus is a voracious blood feeder, and its presence invariably impacts the host’s hematological profile. The severity of the disease is often measured by the degree of anemia it induces. This study established a clear negative correlation between the parasite load (measured by EPG) and critical blood parameters like Hemoglobin (Hb) and Packed Cell Volume (PCV). As the worm burden increases, the host’s oxygen-carrying capacity diminishes, leading to the clinical sign known as “bottle jaw” (submandibular edema) and general lethargy.

“A negative correlation was established between EPG and Hb values. The correlation coefficients in Jamunapari and in Sirohi breed were -0.15 and -0.26, respectively” (Agrawal, 2009, p. 95).

The physiological cost of this infection is high. The host must divert significant energy toward replenishing lost blood cells, which compromises growth and reproduction. The study noted that while Eosinophil counts (associated with allergic/parasitic responses) varied, the drop in PCV and Hb was the most consistent marker of infection severity. Clinically, this validates the use of the FAMACHA system, which assesses anemia levels in the mucous membranes of the eye to identify animals requiring treatment, thereby slowing the development of drug resistance.

Student Note / Exam Tip: A strong negative correlation exists between Faecal Egg Counts and Hemoglobin/PCV values, serving as a primary indicator of Haemonchosis.

Parameter	Jamunapari (Mean)	Sirohi (Mean)	Correlation with FEC
PCV (%)	20.81 ± 0.67	19.16 ± 0.65	Negative
Hb (g/dl)	7.51 ± 0.20	6.56 ± 0.20	Negative
Eosinophils (%)	2.61 ± 0.59	3.19 ± 0.58	Variable

Fig: Hematological profiles and their relationship with parasitic load (Reformatted from Agrawal, 2009, Table 16 & 17).

Professor’s Insight: Pathophysiologically, the anemia caused by H. contortus is hemorrhagic; understanding this helps differentiate it from nutritional anemias in diagnosis.

Immunological Responses and Vaccine Potential

Developing a vaccine against Haemonchus contortus infection represents a major goal in parasitology. This study investigated the immune response triggered by two types of antigens: Crude Somatic Antigen (CSA) derived from the whole worm body, and Excretory/Secretory (ES) antigen released by the worm during metabolic processes. The results showed that while both antigens elicited an antibody response, the nature and duration of protection varied, offering clues for future vaccine formulations.

“The group A immunized by CSA experienced the highest antibody level in immunization phase within one week… [However] ES antigen immunized group B experienced a early gradual rise in antibodies titer and remained constant” (Agrawal, 2009, p. 100).

The trial results suggested that while CSA might trigger a rapid spike in antibodies, the ES antigens provided a more sustained immune engagement. This is biologically consistent, as ES products are the “hidden” antigens constantly exposed to the host immune system during active infection. Vaccination trials indicated that immunized goats had reduced egg shedding compared to controls. This reduction in FEC is epidemiologically significant because it lowers pasture contamination, breaking the transmission cycle for the entire herd, not just protecting the individual animal.

Student Note / Exam Tip: Excretory/Secretory (ES) antigens generally provide more specific and sustained immune protection than crude somatic extracts in nematode vaccines.

Professor’s Insight: Vaccine efficacy in parasitology is often measured by reduction in egg output (fecundity) rather than sterile immunity (total prevention of infection).

Real-Life Applications

• Strategic Deworming: Based on the seasonal data, farmers in semi-arid regions should target deworming efforts immediately prior to and during the monsoon season to mitigate the highest larval challenge.
• Selective Breeding: Producers can introduce Sirohi bucks into Jamunapari herds or select replacement stock based on low FEC history to gradually improve the genetic resistance of the flock.
• Anemia Monitoring: Implementing regular FAMACHA scoring (checking eye color) is scientifically supported by the study’s findings on the correlation between PCV and infection intensity, saving money on unnecessary drugs.
• Vaccine Development: Researchers should focus on isolating specific proteins within the Excretory/Secretory (ES) antigens, as these showed more promise for sustained immunity than whole-worm extracts.
• Nutritional Support: Recognizing that infection causes significant blood loss (protein loss), providing protein-rich supplementation during high-risk months can help animals withstand the pathogenic effects of Haemonchus contortus infection.

Key Takeaways

• Haemonchus contortus infection prevalence peaks significantly during the rainy season (Aug-Sept) due to optimal humidity for larvae.
• Sirohi goats are genetically more resistant to natural infection than Jamunapari goats, evidenced by consistently lower egg counts.
• Infection causes a marked decrease in Hemoglobin and Packed Cell Volume (PCV), leading to severe anemia.
• Immunization with ES antigens (Excretory/Secretory) provides a more sustained antibody response compared to Crude Somatic Antigens (CSA).
• Peri-parturient rise (PPR) in faecal egg counts is observed, meaning lactating does are a major source of pasture contamination.
• Breeding programs should utilize Faecal Egg Count (FEC) as a heritable trait to select for resistant animals.

MCQs

1. Which season recorded the highest prevalence of Haemonchus contortus infection in both goat breeds?
A) Summer
B) Winter
C) Rainy
D) Spring

• Correct: C
• Difficulty: Easy
• Explanation: The study confirmed that high humidity and moderate temperatures during the rainy season facilitate the hatching and survival of infective larvae.

2. Based on the Least Square Means of Faecal Egg Counts (LFEC), which breed demonstrated higher susceptibility?
A) Sirohi
B) Jamunapari
C) Barbari
D) Black Bengal

• Correct: B
• Difficulty: Moderate
• Explanation: Jamunapari goats had consistently higher LFEC values (6.01) compared to Sirohi (5.73), indicating higher susceptibility to the parasite.

3. What is the relationship between Faecal Egg Count (FEC) and Packed Cell Volume (PCV) in infected animals?
A) Positive correlation
B) No correlation
C) Negative correlation
D) Exponential correlation

• Correct: C
• Difficulty: Moderate
• Explanation: As the parasite burden increases (higher FEC), the blood volume decreases due to the worm’s feeding habits, resulting in lower PCV (Negative correlation).

FAQs

Q: What is the main clinical sign of Haemonchus contortus infection?
A: Severe anemia is the primary sign, often visible as pale mucous membranes and “bottle jaw” (submandibular edema) due to protein loss.

Q: Why is the Sirohi breed more resistant than Jamunapari?
A: Sirohi goats evolved in arid, resource-scarce regions, likely developing stronger natural resilience and immune mechanisms to survive parasitic challenges compared to the larger Jamunapari breed.

Q: Did the study suggest a vaccine is available?
A: The study conducted experimental trials showing that ES antigens induced immune protection, but a fully commercial vaccine was not the final product; it highlighted the potential for vaccine development.

Q: How does seasonality affect worm control?
A: Larvae survive best in moisture. Control programs must focus on the rainy season to prevent massive herd infection, as dry summers and cold winters naturally suppress larval populations.

Lab / Practical Note

Safety First: When conducting faecal egg counts or copro-culture in the lab, always wear gloves and lab coats. Haemonchus is primarily a ruminant parasite, but faecal samples may contain other zoonotic pathogens. Ensure proper disposal of biological waste after floating eggs in salt solutions.

Sources & Citations

Thesis Citation:
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, pp. 1–121.

Educational Purpose:
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Author Box

Author: Ms. Nimisha Agrawal (PhD Candidate/Scholar at time of publication)
Affiliation: Central Institute for Research on Goats (CIRG), Makhdoom, Mathura, India.

Disclaimer: This content is an educational summary of a specific scientific thesis and does not constitute veterinary medical advice.

Reviewer: Abubakar Siddiq
Note: This summary was assisted by AI and verified by a human editor.