Impact of Haemonchus Contortus on Packed Cell Volume and Goat Physiology

Last Updated: January 22, 2026
Estimated reading time: 7 minutes
Word count: 1420

The clinical manifestation of Haemonchus contortus infection is primarily defined by its voracious blood-feeding activity, which directly impacts the host’s haematological status. For veterinary students and researchers, understanding the relationship between parasitic worm burden and blood parameters like packed cell volume (PCV) is essential for diagnosis and evaluating breed resistance. This post details the significant physiological changes observed in Jamunapari and Sirohi goats, specifically focusing on the varying degrees of anaemia, the correlation between egg counts and blood loss, and the critical phenomenon of immunity loss during pregnancy and lactation.

Key Takeaways:

• Anaemia Indicator: A strong negative correlation exists between faecal egg counts (FEC) and packed cell volume, making PCV a reliable proxy for resistance.
• Breed Resilience: Jamunapari goats maintained higher overall PCV levels than Sirohi goats, yet Sirohi breeds showed less drastic physiological fluctuations under stress.
• Reproductive Stress: The peri-parturient rise (PPR) in parasite eggs was most severe in early lactation, coinciding with significant drops in maternal immunity.
• Eosinophil Response: Eosinophil counts did not differ significantly between breeds, suggesting that cellular immunity markers might be less distinct than haematological ones in these specific populations.
• Seasonal Anaemia: Blood parameters worsened significantly during the monsoon season, aligning with peak larval availability on pastures.

PHYSIOLOGICAL AND HAEMATOLOGICAL CONSEQUENCES OF INFECTION

Haematological Profile: Haemoglobin and PCV

The study rigorously evaluated the blood profile of 267 goats (115 Jamunapari and 152 Sirohi) to quantify the impact of natural Haemonchus infection. The most critical parameters measured were Haemoglobin (Hb) and packed cell volume (PCV), both of which serve as direct indicators of the anaemia caused by the parasite. The results highlighted a clear genetic difference: Jamunapari goats, despite being more susceptible to higher worm burdens, maintained a higher baseline PCV compared to the Sirohi breed. However, both breeds suffered significant declines in these parameters during peak infection periods.

“The overall least squares mean for PCV of animals was 19.98±0.58 percent during the course of infection” (Agrawal, 2009, p. 121).

The data revealed that while age and sex had non-significant effects on PCV, the breed factor was highly significant ($P<0.01$). Jamunapari goats averaged a PCV of 20.81%, whereas Sirohi goats averaged 19.16%. This suggests that Jamunapari goats might have a larger physiological reserve or a higher basal metabolic requirement, which paradoxically might make the clinical signs of anaemia appear later than in breeds with lower baseline values. However, the sharp decline observed post-infection confirms that Haemonchus overwhelms these reserves regardless of the starting point.

Student Note / Exam Tip: PCV (Hematocrit) is the percentage of red blood cells in the blood; a value below 20% in goats often indicates severe anaemia, commonly associated with haemonchosis (barber’s pole worm).

Professor’s Insight: In clinical practice, do not rely on breed averages alone. A “normal” PCV for a Sirohi goat might be considered anaemic for a Jamunapari. Always establish a baseline for your specific herd.

Parameter	Jamunapari Mean ± SE	Sirohi Mean ± SE	Significance
Haemoglobin (g/dl)	7.51 ± 0.20	6.56 ± 0.20	P<0.01
Packed Cell Volume (%)	20.81 ± 0.67	19.16 ± 0.65	P<0.01
Eosinophils (%)	2.61 ± 0.59	3.19 ± 0.58	NS (Not Significant)

Fig: Comparison of haematological parameters between Jamunapari and Sirohi goats under natural infection (Reformatted from Table 16, p. 123).

The Peri-Parturient Rise (PPR)

One of the most biologically significant findings of the thesis was the analysis of the Peri-Parturient Rise (PPR). This phenomenon refers to the temporary loss of acquired immunity to parasites observed in female animals around the time of birthing (kidding) and lactation. The study monitored 1,399 samples across different physiological stages: Dry, Early Pregnant, Late Pregnant, Early Lactation, and Late Lactation. The results showed a dramatic spike in worm egg counts (and a consequent potential drop in packed cell volume) specifically during early lactation.

“The mean LFEC in Jamunapari at Dry, early pregnancy, (EP), late pregnancy(LP), early lactation (EL), late lactation (LL), were 6.17±0.06, 6.32±0.15, 6.44±0.12, 6.34±0.13, and 6.21±0.11 respectively” (Agrawal, 2009, p. 117).

The study noted that while Dry does had the lowest egg counts, Late Pregnant and Early Lactating does had the highest. This relaxation of immunity is attributed to the redirection of nutrients (protein) toward fetal growth and milk production, leaving the immune system “starved.” Interestingly, the Sirohi breed showed a sharper decline in egg counts after the early lactation peak compared to Jamunapari, suggesting a faster recovery of immune competence. This biological insight is crucial for timing nutritional supplements; feeding extra protein during late pregnancy can help maintain the dam’s packed cell volume and immune defenses.

Student Note / Exam Tip: The Peri-Parturient Rise is linked to the hormone Prolactin and protein scarcity. It is the main reason why lactating mothers are the primary source of infection for their new offspring.

Professor’s Insight: The fact that Sirohi goats recover faster from PPR indicates better adaptation to resource-poor environments—a key trait for sustainable breeding in semi-arid zones.

Correlation Between Parasitology and Haematology

To validate the use of blood parameters as a diagnostic tool, the study calculated the correlation coefficients between Faecal Egg Counts (LFEC) and haematological markers. The analysis confirmed a significant negative correlation between the parasite load and the host’s blood health. As the number of parasite eggs increased (indicating higher worm burden), the packed cell volume and Haemoglobin levels consistently decreased.

“The correlation coefficient of relationship between EPG and PCV values were negative i.e. -0.16 and -0.36 in Jamunapari and Sirohi goats, respectively” (Agrawal, 2009, p. 123).

This negative correlation was stronger in Sirohi goats (-0.36) than in Jamunapari (-0.16). This suggests that in Sirohi goats, the egg count is a very tight predictor of anaemia, whereas in Jamunapari goats, other factors (perhaps body size or nutritional reserves) might buffer the blood values slightly, making the correlation weaker. Conversely, the correlation between PCV and Hb was extremely high and positive (0.73 to 0.57), confirming that both metrics are equally valid for assessing the severity of anaemia in the field.

Student Note / Exam Tip: A negative correlation means that as one variable goes up (Worms), the other goes down (PCV). This statistical relationship underpins the logic of the FAMACHA eye-color chart used globally.

Professor’s Insight: The weaker correlation in Jamunapari goats implies that you might see high egg counts in this breed before you see a severe drop in PCV—early diagnosis via faecal testing is therefore more critical for this breed.

Eosinophilia: A Less Reliable Marker?

Eosinophils are white blood cells typically associated with fighting parasitic infections. The study attempted to use peripheral eosinophil counts as a marker for resistance. However, unlike packed cell volume, the eosinophil data showed high variability and no statistically significant difference between the resistant Sirohi and susceptible Jamunapari breeds. The mean eosinophil percentage was 2.61% for Jamunapari and 3.19% for Sirohi.

“The factors like sex had non-significant effect for eosinophils of animals” (Agrawal, 2009, p. 109).

This finding contradicts some literature that suggests resistant animals always have higher circulating eosinophils. The thesis posits that tissue-level eosinophilia (in the gut lining) might be more relevant than blood eosinophilia, or that the specific strains of goats in this semi-arid region utilize different immune pathways. Therefore, while eosinophilia is a general sign of parasitism, it is not a precise tool for distinguishing between resistant and susceptible individuals in these breeds.

Student Note / Exam Tip: Eosinophilia is a hallmark of helminth infections, but its levels in peripheral blood can fluctuate wildly and may not always correlate with resistance status in every breed.

Professor’s Insight: Do not discard eosinophils entirely, but prioritize PCV and FEC for selection decisions. Eosinophils are part of the “Th2” immune response, but their presence in blood is transient compared to their accumulation in tissues.

Real-Life Applications

1. Field Diagnostics: Understanding the strong correlation between FEC and packed cell volume allows field vets to use PCV (via micro-hematocrit centrifuge) as a quick, cheap proxy for worm burden when faecal analysis is unavailable.
2. Targeted Nutrition for Dams: The identification of the PPR occurring specifically in late pregnancy and early lactation provides a clear window for intervention. Farmers should increase protein rations 4 weeks pre-kidding to prevent the drop in PCV and immunity.
3. Breed-Specific Reference Ranges: The study establishes different “normal” blood values for Jamunapari and Sirohi. Vets can avoid misdiagnosing anaemia in Sirohi (who naturally have lower PCV) by using breed-specific baselines.
4. Selection Criteria: Since PCV is heritable and correlated with resistance, breeders can use “animals that maintain PCV during infection” as a selection criterion, breeding specifically for resilience against anaemia.

Why this matters: Applying physiological data to management protocols moves veterinary care from reactive (treating sick animals) to proactive (preventing the immunity drop), ensuring healthier herds and higher survival rates for kids.

Key Takeaways

• Significant Anaemia: Natural infection causes a measurable drop in Haemoglobin and packed cell volume across all goat breeds.
• Breed Benchmarks: Jamunapari goats naturally have higher Hb and PCV values than Sirohi goats, regardless of infection status.
• PPR Danger Zone: The risk of infection and pasture contamination is highest during early lactation due to the peri-parturient rise.
• Diagnostic Correlation: PCV is a robust inverse indicator of parasite load; low PCV almost always means high worm burden in these breeds.
• Recovery Rate: Sirohi goats recover from the reproductive stress of infection faster than Jamunapari goats, highlighting their adaptability.

MCQs

1. Which physiological stage showed the highest Faecal Egg Counts (FEC) in the study?
   A. Dry period
   B. Early Pregnancy
   C. Late Pregnancy and Early Lactation
   D. Post-weaning
   Correct: C
   Difficulty: Moderate
   Explanation: The study found that FEC peaked during late pregnancy and early lactation due to the peri-parturient relaxation of immunity (Agrawal, 2009, p. 117).
2. What was the nature of the correlation between Faecal Egg Count (FEC) and Packed Cell Volume (PCV)?
   A. Positive correlation
   B. Negative correlation
   C. No correlation
   D. Variable correlation
   Correct: B
   Difficulty: Easy
   Explanation: A negative correlation (-0.16 to -0.36) was observed, meaning as worm egg counts increased, the PCV (blood volume) decreased due to blood loss (Agrawal, 2009, p. 123).
3. Which breed showed significantly higher overall Haemoglobin (Hb) levels during the study?
   A. Sirohi
   B. Jamunapari
   C. Barbari
   D. Black Bengal
   Correct: B
   Difficulty: Moderate
   Explanation: Jamunapari goats had a mean Hb of 7.51 g/dl compared to 6.56 g/dl in Sirohi goats (Agrawal, 2009, p. 123).

FAQs

Q: What is the normal PCV range for the goats in this study?
A: The study recorded average PCV values of approximately 20.81% for Jamunapari and 19.16% for Sirohi goats during the course of natural infection.

Q: Why does immunity drop in pregnant goats?
A: Immunity drops due to the “peri-parturient rise” (PPR), where the body prioritizes nutrients for the growing fetus and milk production, leaving fewer resources for the immune system to fight parasites.

Q: Is Eosinophil count a good way to select for resistance in these breeds?
A: The study suggests it is not the best marker, as there was no significant difference in eosinophil counts between the resistant and susceptible breeds, unlike FEC and PCV.

Lab / Practical Note

Lab Tip: When measuring PCV using a micro-haematocrit centrifuge, always seal the capillary tubes securely with clay and balance the centrifuge rotor. Read the PCV percentage immediately after spinning to prevent the red cells from unpacking, which would give a falsely high reading.

External Resources

• NCBI: Pathophysiology of Haemonchus contortus
• ScienceDirect: Peri-parturient rise 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 109, 117, 121, 123.

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, PhD, Zoology

textbook scientific diagram + modern infographic; white background; labeled parts; aspect ratio 16:9; include alt text: Graph showing the inverse relationship between Faecal Egg Count (rising line) and Packed Cell Volume (falling line) in goats, annotated with anaemia threshold.