Studies On The Morphology, Biology And Pathogenicity Of Knemidokoptes Mutans

The paper deals with the morphology, biology and pathogenicity of K.mutans (Robin, 1860).There are four developing stages in the life cycle of K.mutans , i.e. egg, larva, nymph and adult. The female has two nymphal stages and male has one nymphal stage. The sizes of every developing stage were measured and the morphology of them was described under LM. From the experiment data, the following conclusions can be drawn. Male adult* s size is 150.6 + 9.6x95.7 + 7.7um, oral in shape, long feet, two long setae at the bottom of the body. Female adult' s size is 290.4+22.5 x 236.3 +22.6um, globular in shape, short feet, two long setae at the bottom of the body. Larva' s size is 125.6+ 12.9x91.7+ 14.4um, oral in shape, 6 feet, two setae at the bottom of the body. Nymph 1' s size is 133.1 +16.2x 112.3 + 14.4um, oral or round in shape, 8 feet, without seta at the bottom of the body. Nymph 2' s size is 185.1+24.0x153.9+ 25.6um, oral or round in shape, 8 feet, two setae at the bottom of the body.Male nymph' s size is 137.9+ 15.0X91.1 ?.1 Mm, being similar to the adult male in the external structure. Egg' s size is 155.2+19.8x110.4+ 16.9um, oral in shape, thin egg shell, rufous, smooth and transparent Careful observation on the ultrastructure of K.mutans with scanning electron microscopic is first reported. The ultrastructure of K.mutans, including suckers, genital pore, protrusions, setae and mouthpart is recounted. From the experiment data, the following conclusions can be drawn: 1) Larva has campanulate sucker at the tip of every foot; handle of the sucker is nonarticulate. There is a quadrate notum and no procreation area at the bottom of the body. 2) There is no sucker at the tip of female' s foot. 3) Nymph is similar to the adult female in the external structure. 4) Genital pore of the male is round in shape with two setae around it.The effects of temperature and pH on survival of off-host K.mutans have been studied. The determinate temperature were 14C, 4C, 25C and 40C and the determinate pH were 4, 5, 7 and 8. The results showed that the maximum survival time of the off-host K.mutans was 48h at 40C, 108h at 25C, 228h at 14C and 144h at 4C successively. The results also showed that the maximum survival time of the off-host K.mutans was 120h at pH 4, 132h at pH 5, 96h at pH7and 96h at pH8 successively. The result from the study on the subset distribution of every developing stage of K.mutans showed as follows. Number of larvae and female adults are the most, the second is that of female nymphs are, the next is that of maleadult, number of male nymphs and eggs are the least.The symptoms and pathological changes of chickens infected with K.mutans were studied. This disease is characterized by swellings, encrustations, bleeding, skin thickening and lesions on the bare parts of the legs and feet. On occasion, chicken also showed clinical signs of itching, eating feather and eating eggs. Pathological changes mainly include thickening corneum, hyperkeratosis and calcification. There were a certain number of K.mutans in the stratum corneum. Cells in the stratum granusum and stratum germinativum reduced and thickened evidently. There were degeneration, necrosis and nucleus karyolysis in some cells. Some mites immerged into the deep epidermis and then resulted in severe dermatitis in stratum spongiosum and stratum compactum of dermis. Pathological changes in Stratum spongiosum include loosing, swellings, aggregates of lots of mononuclear cells and eosinophilic heterophils, vascular congestion and oedema, pigmentation. Stratum compactum of dermis is characterized by aggregates of a certain number of mononuclear cells, vascular congestion and oedema.