Types of Pathogens

It is natural that the best-known pathogens are those that cause epizootics in economically important insects and show potential for use in microbial control of pest species. In this short account, the major features of some of these pathogens will be outlined, as a basis for the discussion on microbial control presented in Chapter 24, Section 4.3.1.

5.2.1. Bacteria

Many species of bacteria have been shown experimentally to be highly pathogenic should they gain access to the body cavity. However, under natural conditions, the maaority of these never cause epizootics (even though their infectivity is high) because of the barrier presented by the integument and lining of the gut. Further, the gut may be unsuitable for survival and multiplication of the bacteria because of its pH or redox potential, or because of the presence within it of antibacterial substances or antagonistic microorganisms. Infection of an individual insect occurs when the integument or gut is physically damaged. The commonest route of invasion appears to be via the midgut. Bacteria are sometimes able to slip between the peritrophic matrix and the midgut epithelium at either the anterior or the posterior end of the midgut, or through ruptures in the matrix caused by the passage of food along the gut.

The subsequent mode of action of the bacteria, that is, how they cause a pathological condition, is varied. Invasion and destruction of the midgut epithelium is typically the first step, and for some bacteria this may be their only activity, their host then dying of starvation. More often, bacteria not only destroy the midgut epithelium but then grow rapidly in the hemolymph and other tissues, causing massive septicemia. Others act by toxemia; that is, they liberate toxins that kill the host's cells. Other bacteria become pathogenic only when they are able to enter the hemocoel via lesions in the midgut epithelium caused by other microorganisms such as protozoa, viruses, and nematodes.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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