Behavioral effects of lead and Toxocara canis in mice.

Adult mice were administered the common parasite Toxocara canis or lead or both. The parasite clearly altered mouse performance on tests of exploration, activity, learning, and motor coordination; behavioral effects in mice receiving lead alone were less general. Consequence of Toxocara administration appeared attenuated in animals receiving both agents. Parasite larvae were found in the central nervous system in all infected mice.

Cancer experience among coke by-product workers.

This paper presents the site-specific cancer mortality, 1953-1966, for men employed in by-product coke plants in Allegheny County, Pa. Approximate relative risks, which take into account race, age, and calendar years of follow-up, have been calculated for various work areas of the coke plant. The major findings are: 1. As indicated previously by Lloyd and Redmond, men with five or more years at the coke ovens have an excess risk of dying from lung cancer and kidney cancer. 2. Cancers of the digestive system are significantly elevated in nonoven workers. Cancers of two sites, the colon and pancreas, account for the total excess in cancers of the digestive system. 3. Cancers of the buccal cavity and pharynx appear high in nonoven workers, although the number of deaths involved is small. These observations clearly indicate the need to consider nonoven as well as oven workers when evaluating cancer hazards in the coke plant.

Pica patterns, toxocariasis, and elevated blood lead in children.

Blood samples were obtained during a lead screening program from 100 children aged 1-6 years in Allegheny County, Pennsylvania, to determine whether there was any association between specific forms of pica and infection with Toxocara canis, the principal cause of visceral larva migrans in the United States, or elevated blood lead levels. Significant associations were found between: 1) feces, soil, or grass pica and Toxocara infection; 2) paint or plaster pica and elevated blood lead; and 3) dog ownership and Toxocara infection. These findings suggest that an accurate pica history may be useful in identifying potential health problems in children.

Epidemiological characteristics and clinical findings in patients with serologically proven toxocariasis.

The enzyme-linked immunosorbent assay (ELISA) using Toxocara canis larva-specific antigens was used to confirm a presumptive clinical diagnosis of visceral larva migrans in patients whose serum specimens were submitted to the Center for Disease Control. The clinical and epidemiological characteristics of patients with diagnostic ELISA titres (greater than or equal to log2 5) were compared with patients who had less or no detectable antibody. The typical patient with serologically confirmed toxocaral visceral larva migrans was about five years of age and resided in the southern half of the USA. Clinical findings were likely to include leucocytosis, eosinophilia, an increased anti-A or anti-B isohaemagglutinin titre, and an elevated serum IgG level. Pica, as ascertained by a physician questionnaire, was not a consistent finding and both sexes were nearly equally represented.

Neuropathological studies of experimental toxocariasis in lead exposed mice.

Binghamton Heterogeneous stock mice intubated with embryonated eggs from the common parasite of dogs, Toxocara canis, display dramatic alterations in behavior. Many of these behavioral changes are markedly attenuated if mice are maintained also on a drinking solution containing lead acetate. The data presented here, however, show that the extensive neural degeneration of the CNS occurs after T. canis infection and that the nature and extent of this degeneration is similar, regardless of whether mice had been administered parasites alone or in combination with lead. Thus the neuropathological data reported in detail here cannot account for the striking interactive influence of T. canis and lead on behavior.

Toxocara canis and lead alter consummatory behavior in mice.

Ingestion of palatable and unpalatable solutions was measured in adult mice in which had been administered the common parasite of the dog, Toxocara canis alone, or in combination with lead. In addition, response to hot plate and susceptibility to electroconvulsive seizure were also measured. Results from the palatability test indicated that either lead or Toxocara may alter the mouse's mode of interacting with its environment. However, the two agents in combination interacted in their effects on consummatory behavior. Results from the hot plate and ECS measures were less clear with respect to how lead and/or Toxocara influence temperature reactivity and seizure susceptibility. Histological examination of the CNS in parasite infected animals revealed Wallerian Type degeneration of fiber pathways including the corpus callosum, olfactory tract, and cerebellar penduncles.

The impact of single versus repeated exposure of mice to Toxocara canis.

Infection with T. canis can alter dramatically the brain and behavior of the host. Previous results suggest that if the mammalian host is exposed either simultaneously to lead, or has a history of prior exposure to that toxic substance, the magnitude of the behavioral reaction to T. canis may be modified or even reduced. The present data suggest that the magnitude of both the behavioral and tissue/immune reactions may be less if the organism has multiple, instead of a single exposure, to T. canis. Lead, and perhaps other environmental toxicants may alter neurotropic products of the parasite, the behavior of the parasite, and/or reactivity of the host in the presence of the parasite. Such considerations may help explain, in part, the relative rarity of reported toxocariasis in humans, despite the fact that serological indices suggest that exposure to T. canis may be as high as 7% of the world population.

Heligmosomoides polygyrus (=Nematospiroides dubius): the development of self-cure and/or protection in several strains of mice.

Strains of outbred (ICR/CD1 and S--W) and inbred (BALB/C and C57BL/6) mice vaccinated subcutaneously (SQ) with 500, 1,000, or 2,000 exsheathed Heligmosomoides polygyrus larvae developed varying levels of protection upon subsequent oral challenge with larvae. In contrast, the inbred C3H/HEJ strain failed to develop protection at any dosage level tested. ICR/CD1 mice vaccinated intraperitoneally with exsheathed larvae developed a high level of resistance but exhibited extensive adhesions of the viscera. When ensheathed larvae were used for vaccination, ICR/CD1 mice developed a moderate level of protection; but 1% of the vaccine dose was recovered in the intestine as adult stages. Both the inbred and outbred strains given multiple oral infections developed a protection response similar to that strain's response following parenteral vaccination. The specificity of this protection was demonstrated using various complex foreign antigens. In contrast, the self-cure response was observed only in the S--W strain.

Influence of immunizing dose and presence or absence of adult worms on the development of resistance to Nematospiroides dubius challenge infections of mice.

H-2 congenic strains expressing resistant (H-2q, H-2f) or susceptible (H-2k) haplotypes were compared for their ability to resist challenge infection with N. dubius following a 6- or 14-day ivermectin-abbreviated immunizing infection. B10.BR mice (H-2k) were considerably more resistant to infection when the priming interval was shortened from 14 to 6 days. B10.Q (H-2q) and B10.M (H-2f) mice resisted challenge regardless of which immunization regimen was used. The influence of parasite numbers on the response to challenge was studied by comparing infections in resistant DBA/1 (H-2q) and susceptible CBA/J (H-2k) mice that differ at both H-2 and non-H-2 genes. DBA/1 mice, immunized with 50 or 150 L3 of N. dubius for 14 days, resisted challenge, whereas mice receiving 300 worms did not. In contrast, CBA/J mice failed to resist challenge at all priming doses tested. When the immunizing infection was shortened from 14 to 6 days, DBA/1 mice resisted challenge regardless of priming dose and CBA/J mice resisted challenge only when the highest dose of 300 worms was used for priming. The data suggest that susceptible strains of mice may be preferentially immunosuppressed, particularly at low infective doses, and that suppression is associated with adult worms present in the lumen of the small intestine.

In vivo and in vitro egg production by Nematospiroides dubius during primary and challenge infections in resistant and susceptible strains of mice.

Experiments were conducted to examine adult worm burdens, fecal egg output, and in vitro fecundity of Nematospiroides dubius in resistant LAF1 and susceptible CBA mice 12, 15, 18, and 21 days following primary and challenge infections. A strong correlation was obtained on the number of eggs produced by worms cultured in vitro and the egg production as assessed by fecal egg count. Worm counts, fecal egg counts, and in vitro fecundity were similar on all days studied following a primary infection in both mouse strains. However, after challenge infection, LAF1 mice showed lower worm burdens, fecal egg output, and in vitro egg production when compared to CBA mice. Although the egg production of surviving female worms from immune LAF1 mice was decreased, it never fell below a threshold of 100 eggs/day. The reduced fecundity may be a manifestation of a general anti-worm response rather than responses directed specifically at worm reproduction.

Immunity to Nematospiroides dubius: parasite stages responsible for and subject to resistance in high responder (LAF1/J) mice.

In the LAF1/J mouse strain, a single prior exposure to infective larvae of N. dubius given per os resulted in greater than 90% reduction of an homologous larval challenge; in contrast, a single larval sensitizing infection had no effect on adult worms introduced directly into the duodenum via laparotomy. The LAF1/J mice given a single sensitizing infection of adult worms via laparotomy did not exhibit resistance to homologous challenge of either infective larvae or adult worms. Because all sensitizing infections were removed chemotherapeutically before administration of challenge inocula, potential effects of "overcrowding" on establishment or development of challenge infections were precluded. Worm-specific antibody determinations indicated that adult worms introduced into the gut lumen did not prime the host for a secondary response to a challenge by larval or adult worms. However, a challenge with larvae of mice previously sensitized with an homologous larval infection, did stimulate an anamnestic antibody response. Collectively, the data indicated that in a highly responsive mouse strain (LAF1/J), larval stages were requisite in stimulation of host resistance to reinfection and a larval challenge was fully susceptible to the effects of that response. Mature adult worms apparently did not stimulate nor were they susceptible to the host's immune response.

Specific antibody levels in the serum of Heligmosomoides polygyrus-infected mice.

Sera from ICR/CD mice were assayed by radial immunodiffusion following oral infection and challenge with Heligmosomoides polygyrus larvae. Infection of these mice was found to alter the concentrations and classes of immunoglobulins, as well as the levels of antiparasitic antibody. Challenge of single- or multiple-infected mice with viable larvae resulted in the appearance of anti-H. polygyrus IgA and IgG in the serum. The kinetics of the detection for both of these antibody classes were consistent with an anamnestic response to an antigen isolated from adult nematodes. There also appeared to be an association in resistant mice of serum IgA levels with early and late events in the life cycle of the parasite.

A survey of susceptibility to infection with Trichinella spiralis of inbred mouse strains sharing common H-2 alleles but different genetic backgrounds.

Twenty-eight different inbred strains of mice representing five different H-2 haplotypes were compared for degree of susceptibility to a primary infection with Trichinella spiralis. Marked differences in susceptibility, measured by the average number of muscle larvae per host, were seen among strains of mice sharing common H-2 alleles. The genes controlling these differences must therefore map at loci outside the major histocompatibility complex. Strains of mice sharing the H-2k haplotype were generally more susceptible than strains expressing other haplotypes and strains expressing H-2q alleles were most resistant. Strains of mice were ranked in order of decreasing susceptibility. Knowledge of these ranking may be of value to researchers wishing to select strains of mice appropriate for studies on T. spiralis.

Epizootiologic patterns of diabetes mellitus in dogs.

A case-control study of spontaneous diabetes mellitus in dogs was undertaken, using 2 veterinary data bases. The Veterinary Medical Data Program (VMDP) contained records of 1,019 cases of canine diabetes from 14 university-affiliated veterinary hospitals. The Animal Medical Center (AMC), a private veterinary hospital which has not participated in the VMDP, contained records of 449 diabetes cases. Each data base was analyzed separately, control groups being chosen from all admissions, excluding diabetic animals. Summary odds ratios by sex adjusted for age and breed indicated significantly (P less than 0.05) elevated risks for entire females and neutered females compared with that for entire males. The VMDP data indicated a significantly elevated risk for castrated males, whereas the risk derived from AMC data was not significantly different from 1. Analysis of risks by breed adjusting for age and sex identified Poodles as being at significantly excess risk, and German Shepherd Dogs, Cocker Spaniels, Collies, and Boxers at significantly decreased risk in both data sets. The male-female risk ratio changed with age from 1 at less than 1 year of age to a predominance of females at older ages. In the AMC data base, diabetes was significantly associated with cataracts in dogs of both sexes combined. Diabetes was also significantly associated with benign mammary tumors in female dogs.

Enzyme-linked immunosorbent assay for measurement of antibody responses to Dirofilaria immitis in experimentally infected dogs.

The chronology of the antibody response to Dirofilaria immitis was measured in 2 groups of experimentally infected Beagle dogs. An enzyme-linked immunosorbent assay (ELISA), using a semipurified, adult D immitis-derived antigen was used to quantitate antibody levels. Group A consisted of 4 dogs inoculated once with D immitis infective larvae, 4 dogs inoculated twice with D immitis infective larvae, and 4 noninoculated dogs. Group B consisted of 26 dogs which were all infected with D immitis; however, 16 of these were given daily prophylactic concentrations of diethylcarbamazine (DEC) beginning 5 days before inoculation. Significant levels of antibody were demonstrable 16 weeks after inoculation of group A dogs and remained significantly increased throughout the study. There were no significant differences in antibody levels in dogs inoculated once or twice. Nontreated and diethylcarbamazine-treated dogs in group B developed significant antibody titers 11 weeks after inoculation. Significant differences in antibody titers between treated and nontreated dogs were first observed 13 weeks after inoculation; these differences remained for the duration of the investigation. There was no apparent correlation between antibody levels and either adult worm numbers or microfilaria counts.

The Malaria Research and Reference Reagent Resource (MR4) Center--creating African opportunities.

The Malaria Research and Reference Reagent Resource Center (MR4) is a program to support the international malaria research community. The primary goal is to improve access to well-characterized quality-controlled parasite, host and vector reagents for standardization of assays and other general research purposes. MR4 is open to all scientists worldwide, however many of its inaugural activities will have a focus in Africa, where the concept for the MR4 was born. Reagents are donated to the MR4 Center by malaria researchers and their institutions for distribution to other investigators special arrangements are also possible for developing reagents in-house, or for coordinating reagents for multi-site studies. In addition to providing reagents, the MR4 also aims to promotoe technology transfer and to foster scientific exchange between new and established malaria researchers. This will be done via workshops, training programs, and dissemination of information (electronic and hard copy). Suggestions for reagents, information resources, or training opportunities are welcome from the research community to make this a responsive, service-oriented program.