J. Frederick Bell

Effects of limb disability on lousiness in mice. I. Preliminary studies

Abstract White mice that suffer paralysis of one or more limbs as a sequel of rabies infection develop excessive louse infestations, lacerations, and areas of depilation. The development of large populations of lice on mice disabled by amputation of both rear limbs indicates that this paralytic sequel of rabies had a marked effect on the degree of parasitism. Low level amputation permits depilation by rubbing, but laceration occurs only rarely. In spite of the demonstration of relationship between disability and parasitosis there are other unknown factors which affect the degree of infestation.

CHRONIC SHEDDING TULAREMIA NEPHRITIS IN RODENTS: POSSIBLE RELATION TO OCCURRENCE OF Francisella tularensis IN LOTIC WATERS

Contamination of streams by Francisella tularensis, a fastidious pathogen, was discovered by Miller in Russia.14 Subsequently that contamination was found to be the source of extensive human outbreaks, and to occur as well in North America. Circumstantial evidence supports a hypothesis that infected voles are responsible for the contamination, but when freshly isolated F. tularensis palaearctica is inoculated parenterally, only acute illness and death result whereas long-term contamination of streams would seem to demand a more chronic process. Laboratory studies have demonstrated that voles have an apparent predilection to tularemic nephritis when partially immunized before parenteral infection, but also when naive voles are infected orally. Associated chronic bacteriuria would seem to fulfill requirements for protracted contamination of watersheds.

Effects of limb disability on lousiness in mice III. Gross aspects of acquired resistance

Abstract Studies of louse populations on partially disabled mice kept individually to prevent mutual grooming have demonstrated that after initial exposure to the parasite, subsequent populations were limited because of development of acquired resistance by the mice. During these experiments it was established that a long period of intensive exposure is required for full development of the resistant state. Further, based on a limited period of observation, the inhibitory function appears to be limited to the exposed site rather than generalized over the entire body. Although detritus that accumulates in a region heavily infested with lice was not a major factor in the resistance to reinfestation that was noted, it could not be eliminated as a minor one. The successful feeding of larval ixodid ticks on louse-resistant mice in a single experiment indicated that the resistance is probably specific for lice.

Effects of limb disability on lousiness in mice. II. Intersex grooming relationships

Abstract Mice that are handicapped as a result of hindlimb disability or amputation develop very large louse burdens when kept separately, but when kept in groups mutual grooming frees them of lice. The most rapid reduction of established louse populations occurred when male mice were placed with female mice. The most efficient grooming took place when one member of a pair was normal and uninfested. Compatibility influenced the grooming reaction, especially in male twosomes. Litter mates kept together were most uniform in reciprocal grooming reactions. Mutual grooming was a life-saving activity among animals overwhelmed by lice as a result of artificially induced postinfectious paralysis. It is postulated as a factor of importance in the parasite-host relationship in wild rodents.

Rabies Vaccine freed of the Factor causing Allergic Encephalitis.

Summary A method has been presented for the removal from rabies vaccine of the factor which causes allergic encephalomyelitis. This factor is not removed by extraction with benzene and ether, but preliminary treatment of the vaccine with these solvents facilitates separation by subsequent treatment. The presence of calcium acetate prevents the loss of antigen when the vaccine is washed. It does not prevent removal of the encephalitic factor which appears to be water soluble. About one-half of the total nitrogen of the vaccine is removed by this washing process. The technic may be briefly summarized as follows: 1. A suspension of infected brain in water is dried from the frozen state. 2. The dried brain is extracted with benzene followed by ether (Live virus may be killed in this stage by heating in benzene). 3. After removal of the ether the dried brain is suspended in distilled water. 4. Sufficient solution of calcium acetate is added to make final concentration of M/10 calcium acetate, and the suspension is permitted to stand in the cold for an hour or two. 5. The calcium acetate solution is removed by centrifugation or filtration and the sediment is resuspended in distilled water to the original volume with agitation (clumps of sediment must be broken up). 6. The distilled water is removed by centrifugation or filtration. 7. The sediment is resuspended in distilled water or saline and homogenized. This is the washed vaccine.

Effects of limb disability on lousiness in mice. IV. Evidence of genetic factors in susceptibility to Polyplax serrata.

Abstract When amputee mice were infested with lice ( Polyplax serrata ) Burm. and kept individually, most of them rapidly developed comparable louse populations. However, certain mice appeared to resist development of louse populations. Several strains of mice were tested and a wide range in susceptibility to infestation with lice was found. The greatest number of lice developed on C57BL/6JN mice and the smallest number on mice of the CFW strain. Those strains of mice that supported the largest number of lice had the greatest mortality. The cross breeding of resistant and susceptible strains of mice revealed evidence of a genetic mechanism. From these crosses it was established that the sex of the resistant parent may be a genetic factor influencing the reaction of the offspring to louse infestation. Coat color of the mice appeared to influence louse infestations, but these studies were inconclusive. Attempts by selective breeding to enhance the natural resistance exhibited by certain mice were not successful. Nevertheless, progeny of resistant parents were as resistant as the parents.

Allergic Encephalitis Following Dialysate of Brain Tissue

Summary The dialysate of benzene-ether extracted brain tissue is capable of causing signs and lesions of allergic encephalitis in guinea pigs. The material recovered in the dialysate is free of protein and presumably contains only substances of low molecular weight.

DETECTION OF TOXOPLASMA MICROTI IN LIVING VOLES.

Abstract Toxoplasma microti Findley and Middleton is a common protozoan parasite in the brains of microtine rodents in several widely separated areas in North America. It was described from voles in England and has been reported in Europe. We have not succeeded in transmitting this organism to voles, mice, or other laboratory animals. Further study of the organism is partially dependent on recognition of infection in living animals. This has been accomplished with a fair degree of accuracy by direct surgery and observation. When the calvarium is exposed by a slit in the scalp, cysts in the superficial areas of the brain are visible. Mortality from surgery has been negligible.

Benzene-Inactivated Rabies Vaccine

Discussion and Summary The use of benzene-ether extraction as a preliminary step in eventual purification of rabies vaccines has been made a more practical procedure by the demonstration that inactivation of the virus by heating in benzene results in a highly potent vaccine. Thus the necessity for preliminary ultraviolet irradiation has been eliminated.

Polyplax serrata: Effects of limb disability on lousiness in mice: VI. Lack of tolerance after neonatal exposure

Abstract Mice restrained from grooming become heavily infested with lice. Ordinarily the hosts develop resistance to the infestation which results in limitation or extinction of louse populations. However, individual mice, the number depending on breed, die of anemia or, in some cases, become debilitated but survive with continuous heavy louse burdens. A similar condition of tolerance is occasionally seen in domestic animals. Experiments were conducted to determine whether heavy exposure to lice in the neonatal period could induce tolerance to the parasite. When adequate provision was made to prevent mortality from louse infestation, survival and acquisition of resistance developed at the same rate and to the same degree in neonatally exposed and in naive mice.