On the relationship between abomasal electrolytes and some population parameters of the nematodes Haemonchus contortus and Nematodirus battus

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Abstract
Possible relationships between the numbers and development and growth of Haemonchus contortus and Nematodirus battus during concurrent infections and the levels of abomasal pH and Na+ were investigated in 2- to 3-month-old and 8-month-old lambs. The percentage of Haemonchus in the fourth larval stage was found to be positively related to the levels of abomasal electrolytes, while the mean lengths of the worms in the total male and female populations and in the fifth-stage populations were negatively related to these parameters. The numbers of Nematodirus and the mean lengths of worms in the total and fifth-stage populations were negatively related and the percentage of worms in the fourth-stage positively related to abomasal pH and Na+ levels. It is suggested that the changes in abomasal physiology caused by massive infections of Haemonchus directly affect the growth and development of this abomasal parasite. It is also suggested that the changes in the abomasal contents entering the proximal part of the small intestine during such infections of Haemonchus alter the intestinal environment and that this alteration directly affects the course of development of concurrent infections of Nematodirus.