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Pathogenic mechanisms not operating in Eimeria necatrix infections.
Zeitschrift Fur Parasitenkunde (Berlin, Germany)
|January 1, 1975
Summary
This study challenges the alarm reaction hypothesis for Eimeria necatrix coccidiosis in chickens. Evidence suggests parasite inhibition and direct drug effects, not a shock reaction, explain mortality and survival.
Area of Science:
- Veterinary Parasitology
- Avian Pathology
- Immunology
Background:
- Eimeria necatrix causes significant mortality in chickens.
- A hypothesis proposed that death from coccidiosis is due to an alarm reaction, not parasite pathogenicity.
Purpose of the Study:
- To investigate the alarm reaction hypothesis for Eimeria necatrix coccidiosis.
- To examine evidence supporting or refuting the proposed shock reaction mechanism.
Main Methods:
- Chickens were inoculated with E. necatrix oocysts.
- Pre-treatment with cysteamine or 5-hydroxytryptamine was administered.
- Chickens received non-lethal doses before lethal doses.
- Treatment with sulphadimidine was initiated post-inoculation.
- In vivo and in vitro drug effects were assessed.
Main Results:
- Cysteamine/5-hydroxytryptamine reduced mortality by inhibiting parasite excystation, not by neutralizing a shock reaction.
- Pre-inoculation with a non-lethal dose increased mortality, contradicting the hypothesis.
- Sulphadimidine treatment led to survival, indicating mortality is not an irreversible shock reaction.
- Sulphadimidine demonstrated direct anti-parasitic effects.
Conclusions:
- The alarm reaction hypothesis for Eimeria necatrix coccidiosis is not supported by the evidence.
- Mortality appears linked to parasite pathogenicity and host-parasite interactions.
- Sulphadimidine is effective against E. necatrix through direct action on the parasite.