leptospira leave the infected host through urine. 

 They lack protection against drying and direct 

 animal-to-animal spread occurs through urine 

 splash to the eyes and nostrils of another animal. 

 This is most likely to occur in dogs, cattle, and 

 possibly swine. Rodents are a most common source 

 of leptospira. When caught, their voided urine 

 may infect man and contamination of damp forage 

 by rodent urine may cause infection in cattle. 

 Infection by leptospira may not always cause very 

 serious disease, as serological testing of livestock 

 indicates widespread exposure often without ob- 

 servable disease. Some serological types are more 

 virulent for cattle and swine and, more important, 

 cause the carrier problem. One of these, Lepto- 

 spira pomona, occurs with such regularity that, 

 when found in man, a livestock source is immedi- 

 ately sought. Similarly, another serotype, Lepto- 

 spira canicola, occurs in dogs, coyotes, and jackals 

 and these are thought of when outbreaks occur. 

 Most leptospira have rodent sources with some 

 species acting as true carriers. 



The relationship of leptospirosis to water in the 

 infectivity cycle is many times direct; that is, water 

 which is contaminated by leptospira in urine infects 

 by way of water consumed, splashed, or inhaled 

 by man or animals. Birds apparently do not enter 

 into the leptospira cycle. 



An indirect water relationship also exists when 

 mineral composition and pH influences continued 

 motility of voided leptospira. Even if growth and 

 multiplication does not occur, motile leptospira 

 are a threat for some time in this water environ- 

 ment. Thus, most episodes of leptospirosis are 

 traceable to swimming holes, ricefields, and natural 

 waters of definable pH and mineral composition. 

 The source of the leptospira is often relatively re- 

 mote in time and distance which on an epidemio- 

 logical basis indicates prolonged survival and vi- 

 tality in the leptospira. Active programs of study 

 of water survival were carried on in Montana 

 and Washington and have continued in Illinois, 

 Iowa, and Louisiana. In these States, water pH 

 is often neutral or alkaline within the criteria for 

 leptospira motility and survival. For leptospira 

 control, livestock cannot be allowed to wade in 

 water. Indirect contamination of water through 

 sewage is unlikely, although free-living leptospira 

 occur in such an environment. 



Water- plays a vital role in the creation of en- 

 vironments leading to other anaerobic diseases of 

 livestock. The organisms causing these diseases are 

 the Clostridia and are important through spore 

 formation and production of toxins. For the or- 

 ganism, the toxins are probably nothing more than 

 food gathering and survival enzymes, but in the 



animal they cause pronounced nervous system de- 

 rangements, tissue coagulation and liquefaction, 

 blood hemolysis, and food poisoning. Clostridia 

 range through many species, some of which have 

 no destructive characteristics. Although some, such 

 as Clostridium perfringens and CI. tetani, may be- 

 come adapted to an enteric existence in animals, 

 almost all are soil adapted. Diseases associated 

 with the soil include gas gangrene, botulism, black- 

 leg of cattle, bacillary hemoglobinuria, and tetanus. 

 Rich organic mud, rotting vegetation, and decaying 

 animal matter serve as ready sources of these 

 organisms. Soil in a dried form contains spores, 

 since growth occurs in wet phase where oxygen is 

 reduced through utilization by other organisms. 

 These spores are resistant to heat and canned foods 

 which are not acid or sterile may allow the growth 

 of the Clostridia which cause disease. 



Water management to avoid oxygen depletion 

 serves to control the anaerobic problem. Mineral 

 content and pH are undoubtedly important factors 

 but these are very seldom factors which should or 

 could be controlled. A system of dykes and water 

 level management for oxygen control in the Bear 

 River Marshes of Utah has reduced botulism of 

 wild birds. This system may ultimately fail, how- 

 ever, through silting and growth of water vege- 

 tation. Temporary and permanent areas of anaero- 

 bic water environment are dangerous to livestock; 

 some only a few feet wide are found from time to 

 time. These areas of water management on the 

 farm are important, but control is usually tempo- 

 rary and often only after livestock loss from the 

 anaerobic toxins or organisms. Livestock should 

 be barred from consuming blackened water not 

 adequately oxygenated. 



The role of water in dissemination of viruses 

 is confused by the total ecological picture of the 

 several virus-host relationships. Recent advances 

 in virus study and nomenclature has made previous 

 systems of classification obsolete and any criteria 

 for viral pollution of water should recognize these 

 changes. Viruses cannot multiply except in a suit- 

 able living system and a variety of biological 

 phenomena limit this to a very narrow range of 

 host cells. They resemble spore-forming bacteria 

 in that the spore stage does not grow and multiply 

 outside a suitable environment. The resemblance 

 ends here as the bacterial spore returns to a vege- 

 tative form in the presence of nutrients and a 

 suitable environment. In water, the presence of 

 viruses represents a dilution which increases pro- 

 gressively through volume change and degradation 

 of the virus particle. 



The epidemiology of virus infections tends to 

 incriminate direct contact; e.g. fomites, mechani- 



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