. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. CHAPTER IX ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA Insects and Trypanosomiases By trypanosomiasis is meant a condition of animal parasitism, common to man and the lower animals, in which trypanosomes, peculiar flagellate protozoa, infest the blood. Depending upon the species, they may be harmless, producing no appreciable ill-effect, or pathogenic, giving rise to conditions of disease. A number of these are known to be transferred by insects. In order that we may consider more ful
. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. CHAPTER IX ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA Insects and Trypanosomiases By trypanosomiasis is meant a condition of animal parasitism, common to man and the lower animals, in which trypanosomes, peculiar flagellate protozoa, infest the blood. Depending upon the species, they may be harmless, producing no appreciable ill-effect, or pathogenic, giving rise to conditions of disease. A number of these are known to be transferred by insects. In order that we may consider more fully the developmental stage of these parasites within their insect host, it is necessary that we des- cribe briefly the structure of the blood-inhabiting stage. The trypanosomes are elongated, usually point- ed, flagellated protozoa (flg. 136) in which the single flagellum, bent under the body, forms the outer limit of a delicate undulating membrane. It arises near one end of the organism from a minute centrosome-like body which is known as the blepheroplast, and at the opposite end extends for a greater or less distance as a free flagellum. Enclosing, or close beside the blepheroplast is the small kinetonucleus. The principal nucleus, round or oval in form, is situated near the center of the body. Asexual reproductions occurs in this stage, by longi- tudinal fission, the nucleus and the blepheroplast dividing independ- ently of- one another. From the blepheroplast of one of the daughter cells a new flagellum is formed. Among the pathogenic species are to be found the causative organisms of some of the most serious diseases of domestic animals and even of man. It is probable that these pathogenic species secrete. 136. Trypanosome brucei. After Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Riley, Wil
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