COCCTDIOSIS AND ITS TREATMENT

Manawatu Times, Volume 62, Issue 132, 5 June 1937, Page 12

COCCTDIOSIS AND ITS TREATMENT

(By L. W. N. Fitch, Veterinary Laboratory, Wallaceville.)

Coccidiosis is probably the most serious disease of fowls in New Zealand. It occurs in all parts of both Islands, and losses are frequently heavy. There are two main forms, caused by different species of coccidia. One species-attacks young chickens, which may show serious signs of parasitism at the early age of ten days, and this attack, if survived, does not protect them from the second species which affects them as pullets, just at the age when they might be expected to be coming into production. The cause of coccidiosis is a protozoan or unicellular organism of microscopic dimensions, known as a “coccidium.” Its life cycle is of very great biological interest, besides being of practical importance from the viewpoint of control. Coccidia have two methods of reproduction—sexual and asexual. The former enables the parasite to survive apart from its host, while the latter ensuros its rapid multiplication and invasion of its host’s tissues once infection has been achieved.

Life Cycxa Briefly the life cycle of coccidia is as follows: The form found in the excreta is known as the oocyst. This is a small oval or round body which can be seen only with the aid of the microscope. The oocyst is covered with a protective membrane which enables it to withstand -weathering for long periods —up to at least a year under suitable conditions. it will not withstand prolonged drying or sunlight. The oocyst contains a central mass of material known as the nucleus, which, under favourable conditions, divides into four parts (sporocysts), each of which again divides into two parts (sporozoites,). The oocyst with its eight contained sporozoites gains access to the gut of the bird via its food or drinking water, and there the action of digestive juices breaks down the cell wail and the sporozoites are liberated. These latter, being motile, are capable \.t invading the cells lining the wall of the intestine. Once in the ceil the sporozoite enlarges and divides into a large number of small organisms (merozoites) which are liberated into the bowel and infest fresh cells. This is the asexual form of reproduction and that chiefly responsible for the multiplication of the parasites. A variation in the above sequence, however, results in the formation from merozoites which have invaded gut cells of two different forms, one male and the other female. The fertilisation of the former by the latter, after their liberation from the cell into the lumen of the gut, results in the formation of an oocyst, which is the form excreted in the droppings and that responsible for the spread of infection. This represents the sexual form of reproduction. Symptoms ol Coccidiosis The severity of the disease varies widely. In some outbreaks the course may be very acute, with sudden, heavy mortality. In others the course inuy be chronic, with progressive emaciation and losses spread over a longer period. In young chicks the former type usually occurs. The birds suddenly begin to die, the chief symptoms being diarrhoea, with blood-stained droppings. This is very useful in diagnosis of the condition. It is due to the extensive damage done to the lining membrane of the blind guts (there are two caeca in the fowl). In this form of coccidiosis the infection is usually conflued to this rogion. The livers, however, in some cases may be grossly affected, showing extensive mottling. This is due to damage caused by coccidia which have passed from the intestine to the liver via the bile-ducts. On post-mortem the blind guts will often be seen to be fllled with blood-stained material, or even, in very acute cases, with actual blood. In others the caeca may be filled with an offensive-smelling, p.asty, yellowish material. In less acute cases the birds huddle together, become droopy and ruffled, and lose their appetite. Death is less sudden. In older birds the onset is more insidious. The birds become unthrifty and pale. They lose weight and become emaciated, frequently showing a weakness of the legs. As against the case of young chicks, pullets are mainly affected in the upper part of the small intestine (i.e., that part immediately following the gizzard). Here, again, much damage may be done to the bowel wall, but the naked eye changes are not so obvious as in the acute type met with in young chicks. The bowel may be dilated and the lining membrane is covered with a catarrhal exudate, which gives it a rough, fluffy appearance when compared with the normal. Treatment It will be clear from the life cycle that there are two points at which wc might direct our attack. The first is while the parasite js in the gut of its host, and the second is the sexual stage —the oocyst, which is excreted in the droppinggs. It has long been realised that the first form of approach was of very limited value. Coccidia in the bowel are very resistant to drugs. Recently, however, two forms of medicinal treatment have been fairly widely advocated, and where more strenuous methods are impracticable, or conditions suitable, those might be attempted. The first of these measures consists of feeding large amounts of milk, the Idea being, that the contents of tli6 intestines become, more acid than usual, and thus the development of the infection is checked. The second involves the use of iodine. This is given in combination with milk, as follows:—lodine, 1 part; potassium iodide, 2 parts; water, 50 parts. This forms the stock solution which is prepared for use by mixing with fresh or skim-milk in the proportion of 1 part, of stock to 3 parts of milk. This mixture is heated gently until it becomes white and added ad lib. to the drinking water. The iodine-milk mixture should bo made fresh daily. It wil lbe realised readily that the above measures only benefit the birds treated, and actually they only assist these* to a limited extent. The birds still continue to excrete infective material, and it is at this stage that

we must direct our efforts. Affected birds constitute a great danger, as they provide a source of re-infection for other birds. It cannot be too strongly stressed that prevention of infection is by far more important in the control of coo cidosis than are curative measures. Thi source of infection must be removed, or, at least, limited as far as possible. AL obviously infected birds should be do stroyed and buried deeply, or, far pr& ferably, burnt. They are a menace to the rest of tho flock, and must not be kept. This is very important and a point which many poultry-keepers fai. to appreciate. A sick bird is not worth auything in the market, and should b« prevented from doiug any more damage Medicinal treatment is useless in acute cases, as also in advanced chronic cases showing emaciation. It may be of value in those cases of coccidiosis in which a diagnosis has been established in tho laboratory, and where the symptoms are merely unthriftiness, unaccompanied by advanced emaciation. In such cases medicinal treatment should bo combined with preventative methods. Young birds should be reared on wire netting to minimize chances of reinfection from infective droppings. Droppings should be removed and buried deeply, or preferably burnt. This is to bo done every two days, this being the | time required for the oocyst to become infective. Oocysts are very susceptible to heat, dryness, and sunlight. Boiling water with caustic soda, or the blow-lamp, are useful in cleaning brooder houses, shed floors, perches, etc. These may be whitewashed, or, in the case of perches and uprights, painted with boiling tar. Incubators, especially trays, should be washed with a 5 per cent, carbolic acid solution and allowed to dry. Where possible, birds should not be run on infected country. Liming of surface soil and frequent turning to expose oocysts to sunlight is a useful measure. It must be remembered that oocysts may survive in soil under favourable conditions for at least a year. Infected birds should not be removed to •“clean” ground, as they will rapidly contaminate it. Only newly-hatched chickens from “clean” incubators and brooder houses should be put on to such new territory. Where practicable, attendants handling infected birds should have no contack with healthy stock. Where this is impracticable, the attendant should thoroughly wash and disinfect hands and gum boots with a disinfectant solution, such as hypochlorite, before leaving infected premises. In view of tho possibility of eggs becoming contaminated by oocysts while passing through the cloaca, it is desirable to adopt some form of disinfection of egys before incubation. Eggs should be washed in methylated spirits, allowed to dry, and then dipped in perchloride of mercury solution of 1 part in 2000 of water) before setting them. Finally, again it. is desirable to emphasise the necessity for tho most persistent and energetic measures in the campaign against coccidiosis.