Mallein

MALLEIN (from Latin malleus--mule), a preparation made from cultures of the glanders bacillus (see Glanders). M. was discovered in 1890 simultaneously by two Russian veterinarians—Gelman in St. Petersburg and Kallningh in Dorpat; the latter, while working with M., became infected and died of glanders. The historical significance of M. lies in that it was the first agent that made it possible to recognize hidden glanders and thereby placed the fight against this disease on a firm foundation. M. is used exclusively as an allergenic diagnostic agent; for serodiagnosis (as an antigen) or for therapeutic purposes it is unsuitable.-The active principle of M. is heat-stable endotoxins of the glanders microbe, obtained by various methods. The original method of obtaining M. consisted of bacterial masses taken from potato cultures being macerated in water with or without the addition of glycerin, killed by heating, and freed from bacterial bodies by filtration. Although such M., free from foreign impurities, satisfied all requirements, it still did not receive wide practical application due to the painstaking nature and danger of its preparation. Subsequently and to the present time, M. is prepared from cultures of varying ages, grown on meat-peptone-glycerin-broth. For the purpose of possibly complete breakdown of the nutrients of this medium, cultures for Russian M. are kept (according to Kresling) for 8-10 months in an incubator. In other countries this period is reduced to 4-6 weeks. Cultures killed by heating are filtered and used either without further processing (Russian M.) or are concentrated by evaporation to 1/10 of their original volume (French M. -- malleine brute) so as to be rediluted before use with a 0.5% solution of carbolic acid, or finally the filtrate of the glanders culture is poured into a 25-30-fold amount of absolute alcohol, whereby a loose, water-soluble precipitate is obtained, which after drying represents Malleinum siccum. All these preparations retain their activity for many years provided they are stored protected from light.-In healthy animals free from glanders or suffering from other diseases, M. causes no reaction except for transient irritation phenomena at the site of administration. Animals that have been infected with glanders, however, already 2 weeks after infection, respond to the introduction of M. with one or another of the allergic phenomena described below, depending on the method of its application. Only severely exhausted individuals are unable to react to M. despite the presence of the glanders process in them.

Subcutaneous malleinization (the classic method of application) requires preliminary thermometric examination of the test animals for 1 day. Horses with elevated temperature are excluded. The injected dose depends on the preparation; Russian M. is standardized (by determination on healthy and sick horses) in such a way that the dose for an adult horse is 1 cm³. The injection is made under the skin of the neck or preferably under the chest. In horses suffering from manifest or hidden glanders, a twofold reaction occurs: thermal and local. The first must correspond to a certain type. After 6-8 hours, a rapid rise in temperature begins, reaching 40-42°. After remaining at this height with small fluctuations for several hours, the curve slowly returns to normal (fig. 2). The local reaction consists in the appearance in the subcutaneous tissue after 6-10 hours of a sharply defined, dense, hot, painful tumor (infiltrate) not less than 15 cm in diameter, which gradually softens and expands, and after 3-5 days is resorbed. With any deviation of the reaction from the described type, both in thermal phenomena and in local reactions, the reaction is not considered positive and the diagnosis remains open.-Intradermal (intracutaneous) malleinization was also proposed for diagnostic purposes, but did not receive wide practical application. Schnurer used it to determine the strength of M. The test M. is introduced in different dilutions in an amount of 0.2 cm³ into the thickness of the skin simultaneously with a similar series of standard M. The reaction is assessed by measuring and comparing the sizes of the individual edematous tumors that form at the injection sites.-Skin malleinization, first tested by Vallee, represents a complete analogy to the Pir reaction in tuberculosis. As a diagnostic procedure in horses, skin malleinization did not prove justified, but in some cases it was successfully applied in chronic glanders in humans.-Eye malleinization was first studied simultaneously in France by Vallee and Martel, and in the USSR by Vladimirov and Khomoransky, and at present represents the most widespread diagnostic reaction, especially suitable for mass preliminary examinations due to the convenience and simplicity of its technique. M. is instilled or smeared with a brush into the conjunctival sac, to which horses not infected with glanders respond only with transient insignificant phenomena of irritation of the mucosa, whereas in most obviously sick or suffering from hidden glanders horses, reactive phenomena usually occur after 4-6 hours, lasting on average 24-36 hours and consisting in redness of the conjunctiva, swelling of it and the entire eyelid with the appearance first of a fibrinous exudate, and then of a more or less abundant discharge of whitish viscous pus, which is considered the most characteristic sign.-Intrapalpebral malleinization, proposed in 1914 by the Italian Lanfranchi and widely applied during the world war, combines the reactions of the subcutaneous and eye methods. Introduced into the lower eyelid of the horse, between the skin and the mucous membrane, M. causes a rise in temperature, local tumor, and purulent conjunctivitis. The reaction occurs on average after 10 hours and reaches its maximum development after 24-30 hours. The diagnostic value of M. in general and of its individual methods of application in particular has met and meets with varying assessments. The correctness or incorrectness of the indications of the allergic reaction caused by M. depends on a number of difficult to take into account factors, both biological (exhaustion of the animal, sexual excitement causing a rise in temperature, etc.) and technical (poorly standardized preparation, error in its administration, unsuitable room temperature, etc.). Therefore it is quite rational, as is done in the USSR, where the fight against glanders is based mainly on malleinization, to combine it in doubtful cases with serodiagnosis (agglutination, complement fixation, etc.).