Experimental eradication of pinworms (Syphacia obvelata and Aspiculuris tetraptera) from mice colonies using ivermectin.

A spray administration of ivermectin was evaluated for the treatment of pinworm infection in mice. In this study, a spray of 0.1% ivermectin injectable solution over the entire cage once a week, for three consecutive weeks (one cycle treatment), was effective in eradicating both Syphacia obvelata and Aspiculuris tetraptera from mice under experimental conditions. In addition, no acute toxicity was observed in 105 mothers or 687 neonates treated with ivermectin, indicating that ivermectin does not affect murine reproduction. Finally, we attempted to eradicate pinworms from infected mice in our institute using this method. Two cycles of treatment were administered, with a two-week pause between cycles, resulting in complete eradication for at least one year. Treating mouse colonies with spray ivermectin is inexpensive, safe, requires very little labor and is very effective at eradicating pinworms from mice.     

A cost-effective and efficacious method of pinworm treatment for large colonies of mice

Rodent pinworm infestations are common in modern animal facilities, and treatments to eradicate these nematodes are often costly and labor-intensive. The authors describe a method they developed to treat rodents with ivermectin using the automatic watering system available at their facility. This delivery method proved an efficacious and cost-effective means of eradicating Aspiculuris tetraptera from a large colony of mice. The system might also be used to provide other orally administered agents to mice and other species.     

Efficacy of ivermectin against Syphacia obvelata (Nematoda) in mice

Ivermectin was evaluated against natural and artificial pinworm (Syphacia) infections in mice. Ivermectin given in the diet for 6 days at 0.0005% was 99% effective against both immature and adult worms. A diet level of 0.0004% reduced immature and mature pinworm by 99 and 75%, respectively but 0.0001% was inactive. One oral dose of 2.0 mg/kg was 100 and 97% effective against gravid females and immature worms, respectively. A dose of 1.0 mg/kg was 96 and 66% effective against the same parasitic stages. A similar effect was observed against adult male worms where 94 and 86% were removed by one oral dose of ivermectin at 2.0 and 1.0 mg/kg, respectively.     

Comparison of various anthelmintic therapies for the treatment of Trypanoxyuris microon infection in owl monkeys (Aotus nancymae)

Trypanoxyuris microon is a pinworm that infects New World nonhuman primates, including Aotus nancymae. Although it typically is clinically insignificant, infection may serve as a significant variable during experimental data analysis. In this study we sought to determine the most effective anthelmintic therapy for eradication of T. microon infection in A. nancymae. Animals confirmed to be infected with T. microon by perianal tape test were treated twice (on days 0 and 14) with pyrantel pamoate, ivermectin, or thiabendazole and evaluated for eggs by daily perianal tape test throughout the entire 28-d period. Successful clearance of eggs was defined as 5 consecutive negative perianal tape tests. Pyrantel pamoate and ivermectin were significantly more effective at egg clearance than were thiabendazole and no treatment. Overall, 100% of the pyrantel pamoate and ivermectin treatment groups were cleared of infection after 2 treatments, whereas only 60% of the thiabendazole group became negative for pinworm eggs. In addition, the time after treatment until clearance was 1 to 2 d for pyrantel pamoate, 2 to 4 d for thiabendazole, and 4 to 6.5 d for ivermectin. These results indicate that pyrantel pamoate was the most effective and rapidly acting anthelmintic for the treatment of adult T. microon infection, with ivermectin as a suitable alternative. However because of the potential for continued development of immature stages or reinfection, anthelmintic doses should be repeated after 1 to 2 wk, in combination with effective environmental sanitation.     

Behavioral effects of ivermectin in mice.

BACKGROUND AND PURPOSE: Ivermectin is a common anthelmintic drug, widely used in laboratory rodents for treatment of pinworm and mite infestations. We evaluated the action of ivermectin on sensitive behavioral tasks in mice during treatment for mites within a barrier facility. METHODS: A total of 21 (5 males, 16 females) mice (129/SvEv) were used for measuring body weight, open field locomotor activity, and rotarod motor coordination. For acoustic startle and prepulse inhibition, 20 C57BL/6J and 29 AKR/J mice were studied. For the Morris water task, the same 20 C57BL/6J mice were studied. Ivermectin (0.08% sheep drench) was administered in the drinking water of the home cage for 8 weeks. Control groups received normal tap water in identical bottles. RESULTS: Ivermectin did not affect general health, body weight, motor coordination, swimming behavior, or spatial learning in several inbred strains of mice. However, it induced a small but significant effect on some sensitive behaviors. CONCLUSIONS: A cautious approach to initiating ivermectin treatment in mice should be used for sensitive behavioral experiments.     

Use of chromosome substitution strains to identify seizure susceptibility loci in mice

Seizure susceptibility varies among inbred mouse strains. Chromosome substitution strains (CSS), in which a single chromosome from one inbred strain (donor) has been transferred onto a second strain (host) by repeated backcrossing, may be used to identify quantitative trait loci (QTLs) that contribute to seizure susceptibility. QTLs for susceptibility to pilocarpine-induced seizures, a model of temporal lobe epilepsy, have not been reported, and CSS have not previously been used to localize seizure susceptibility genes. We report QTLs identified using a B6 (host) × A/J (donor) CSS panel to localize genes involved in susceptibility to pilocarpine-induced seizures. Three hundred fifty-five adult male CSS mice, 58 B6, and 39 A/J were tested for susceptibility to pilocarpine-induced seizures. Highest stage reached and latency to each stage were recorded for all mice. B6 mice were resistant to seizures and slower to reach stages compared to A/J mice. The CSS for Chromosomes 10 and 18 progressed to the most severe stages, diverging dramatically from the B6 phenotype. Latencies to stages were also significantly shorter for CSS10 and CSS18 mice. CSS mapping suggests seizure susceptibility loci on mouse Chromosomes 10 and 18. This approach provides a framework for identifying potentially novel homologous candidate genes for human temporal lobe epilepsy.     

LACK OF ABNORMALITY IN BRAIN AROMATIC AMINES IN RATS AND MICE SUSCEPTIBLE TO AUDIOGENIC SEIZURE*

The levels of certain amines (catecholamines, 5-HT, and ‘histamine’) and of certain enzymes (tyrosine hydroxylase, tryptophan hydroxylase, ChAc, or AChE) in whole brain or selected brain areas of rats and mice susceptible to audiogenic seizure have been compared with the levels in matched groups of non-sensitive animals. Sensitive groups included both those where susceptibility is inborn and those where it is induced by administration of methionine sulphoximine or thiosemicarbazide. No significant difference was found which could be correlated with susceptibility to audiogenic seizure.     

Genetic and environmental interactions determine seizure susceptibility in epileptic EL mice

Gene identification has progressed rapidly for monogenic epilepsies, but complex gene-environmental interactions have hindered progress in gene identification for multifactorial epilepsies. We analyzed the role of environmental risk factors in the inheritance of multifactorial idiopathic generalized epilepsy in the EL mouse. Seizure susceptibility was evaluated in the EL (E) and seizure-resistant ABP/LeJ (A) parental mouse strains and in their AEF1 and AEF2 hybrid offspring using a handling-induced seizure test. The seizure test was administered in three environments (environments I, II and III) that differed with respect to the number of seizure tests administered (one test or four tests) and the age of the mice when tested (young or old). The inheritance of seizure susceptibility appeared dominant after repetitive seizure testing in young or old mice, but recessive after a single test in old mice. Heritability was high (0.67-0.77) in each environment. Significant quantitative trait loci (QTL) that were associated with environments I and III (repetitive testing) were found on chromosomes 2 and 9 and colocalized with previously mapped El2 and El4, respectively. The El2 QTL found in environment I associated only with female susceptibility. A novel QTL, El-N, for age-dependent predisposition to seizures was found on proximal chromosome 9 only in environment II. The findings indicate that environmental risk factors determine the genetic architecture of seizure susceptibility in EL mice and suggest that QTL for complex epilepsies should be defined in terms of the environment in which they are expressed.     

Genetic influence on increased seizure susceptibility in pregnancy

In previous studies we have reported that flurothyl-induced clonic seizure threshold was significantly reduced in pregnant mice. In the present study eight strains of mice were tested for flurothyl seizure susceptibility during pregnancy in an effort to find one which lacked this trait. Latency to myoclonus, latency to clonus, and the interval between these seizures were measured. Two inbred strains, A/Ibg and BALB/cByJ, were resistant to the pregnancy-associated increase in seizure susceptibility. These strains will be used, along with others which show the increased seizure trait, to investigate the neurochemical mechanisms which underlie the increased seizure susceptibility in pregnancy.     

Increased seizure susceptibility and cortical malformation in beta-catenin mutant mice

Beta-catenin has been implicated in epilepsy because of its altered post seizure expression and the role of Wnt2 signaling in autism. To determine beta-catenin's role in seizure susceptibility, we injected penetylenetetrazol intraperitoneally in beta-catenin cerebral cortex- and hippocampus-specific knockout mice. We then analyzed the latency, number, and duration of four phases of seizure behaviors: (I) non-seizure activity, (II) myoclonic jerks, (III) generalized clonic seizures, and (IV) tonic seizures. The latencies to both death and Phase IV were significantly reduced in mutant mice. Mutant mice also spent significantly more time in Phases III and IV and showed significantly less time in the non-convulsive state (Phase I). Nissl and gold chloride staining indicated that the knockout mice had underdeveloped cortices, lacked a corpus callosum, and were missing hippocampal structures. This suggests that dysfunction of beta-catenin-mediated signaling pathways in mice leads to cortical malformation and increased seizure susceptibility.     

Ontogeny of susceptibility to the convulsant, Ro 5-4864, and its relationship to audiogenic seizure susceptibility in inbred mice

The postnatal development of susceptibility to the convulsant effects of Ro5-4864 (4'-chlorodiazepam) was characterized in two inbred mouse strains (DBA/2J and BALB/c ByJ) which as adults differ markedly in their response to this convulsant. Onset of susceptibility to a dose of Ro5-4864 which caused a high frequency of clonic seizures in adults was observed at 10 days of age in DBA/2 mice, but not until 35 days in BALB/c By mice. At 14 days of age an abrupt increase in susceptibility to Ro5-4864-induced tonic seizures was found in DBA/2 but not BALB/c By mice. Both the peak of tonic seizure susceptibility (21 days) and the time course of its subsequent age-dependent decline closely paralleled the change in audiogenic seizure susceptibility in the DBA/2 strain. PK11195 (40 mg/kg) blocked Ro5-4864 (25 mg/kg)-induced, age-dependent tonic seizures but had no effect on clonic seizure induction in the same mice. These observations establish that both the susceptibility to Ro5-4864 in adult mice and the postnatal time course for development of susceptibility to this convulsant are inherently different in these two strains of mice. The lack of coincidence between the developmental onset of susceptibility to Ro5-4864-induced seizures and the onset of supersensitivity to Ro5-4864-induced tonic seizures during the period of peak audiogenic seizure susceptibility in DBA/2 mice implies that more than one neurochemical mechanism is involved in the ability of Ro5-4864 to induce seizures in this strain. However, the blockade of Ro5-4864-induced tonic seizures by PK11195 suggests that peripheral type benzodiazepine receptors may mediate this effect.     

Correlation between the enhancement of flunitrazepam binding by GABA and seizure susceptibility in mice

Various populations of mice exhibit differential sensitivity to seizure-inducing agents. The relationship of seizure susceptibility to alterations in the GABA receptor complex was investigated in six different populations of mice consisting of four inbred strains (C57BL, DBA, C3H, and BALB) and two selected lines (long sleep and short sleep). Seizure activity was induced by intraperitoneal administration of the GAD inhibitor, 3-mercaptopropionic acid, and latencies to seizure onset and tonus were measured. In naive mice of the same populations, GABA enhancement of 3H-flunitrazepam binding was measured in extensively washed whole brain membranes at several GABA concentrations. Both differential seizure sensitivity to 3-mercaptopropionic acid and differential enhancement of 3H-flunitrazepam binding by GABA were observed in these six populations of mice. Correlational analyses indicated a positive correlation between the degree of GABA enhancement of 3H-flunitrazepam binding and resistance to the seizure-inducing properties of 3-mercaptopropionic acid. These data suggest that genetic differences in sensitivity to seizure-inducing agents that disrupt the GABAergic system may be related to differences in coupling between the various receptors associated with the GABA receptor complex.     

Characterization of febrile seizures and febrile seizure susceptibility in mouse inbred strains

Febrile seizures (FS) are the most prevalent seizures in children. Although FS are largely benign, complex FS increase the risk to develop temporal lobe epilepsy (TLE). Studies in rat models for FS have provided information about functional changes in the hippocampus after complex FS. However, our knowledge about the genes and pathways involved in the causes and consequences of FS is still limited. To enable molecular, genetic and knockout studies, we developed and characterized an FS model in mice and used it as a phenotypic screen to analyze FS susceptibility. Hyperthermia was induced by warm air in 10- to 14-day-old mice and induced FS in all animals. Under the conditions used, seizure-induced behavior in mice and rats was similar. In adulthood, treated mice showed increased hippocampal Ih current and seizure susceptibility, characteristics also seen after FS in rats. Of the seven genetically diverse mouse strains screened for FS susceptibility, C57BL/6J mice were among the most susceptible, whereas A/J mice were among the most resistant. Strains genetically similar to C57BL/6J also showed a susceptible phenotype. Our phenotypic data suggest that complex genetics underlie FS susceptibility and show that the C57BL/6J strain is highly susceptible to FS. As this strain has been described as resistant to convulsants, our data indicate that susceptibility genes for FS and convulsants are distinct. Insight into the mechanisms underlying seizure susceptibility and FS may help to identify markers for the early diagnosis of children at risk for complex FS and TLE and may provide new leads for treatment.     

Genetic and phenotypic analysis of seizure susceptibility in PL/J mice

Epilepsy is one of the most common but genetically complex neurological disorders in humans. Identifying animal models that recapitulate human epilepsies is important for pharmacological studies of anticonvulsants, dissection of molecular and biochemical pathogenesis of epilepsy, and discovery of epilepsy susceptibility genes. We discovered that the PL/J inbred mouse strain is susceptible to handling- and rhythmic tossing–induced seizure. The tonic–clonic and generalized seizures observed after induction were accompanied by abnormal EEGs, similar to seizures observed in EL and SWXL-4 mice. PL/J mice also had an extremely low threshold to electroconvulsive seizures compared to other strains and showed variable sensitivity to pentylenetetrazole-induced seizures. Gross neurostructural abnormalities were not found in PL/J mice. Crosses with the seizure-resistant C57BL/6 J strain revealed semidominant inheritance of the rhythmic tossing seizure trait with low penetrance. F2 progeny indicated that the genetic inheritance of seizure susceptibility in PL/J is non-Mendelian. We crossed DBA/2 J mice, which are resistant to rhythmic tossing seizure but susceptible to audiogenic seizures, to PL/J. We found that seizure penetrance in (DBA/2 J × PL/J)F1 mice was similar to the penetrance in (C57BL/6 J × PL/J)F1 mice but the severity and frequency of seizure were higher in (DBA/2 J × PL/J)F1 mice. The PL/J strain serves as an interesting new model for studying the genetics, neurobiology, and pharmacology of epilepsy.     

Maternal loss of Ube3a produces an excitatory/inhibitory imbalance through neuron type-specific synaptic defects

Angelman syndrome (AS) is a neurodevelopmental disorder caused by loss of the maternally inherited allele of UBE3A. AS model mice, which carry a maternal Ube3a null mutation (Ube3a(m-/p+)), recapitulate major features of AS in humans, including enhanced seizure susceptibility. Excitatory neurotransmission onto neocortical pyramidal neurons is diminished in Ube3a(m-/p+) mice, seemingly at odds with enhanced seizure susceptibility. We show here that inhibitory drive onto neocortical pyramidal neurons is more severely decreased in Ube3a(m-/p+) mice. This inhibitory deficit follows the loss of excitatory inputs and appears to arise from defective presynaptic vesicle cycling in multiple interneuron populations. In contrast, excitatory and inhibitory synaptic inputs onto inhibitory interneurons are largely normal. Our results indicate that there are neuron type-specific synaptic deficits in Ube3a(m-/p+) mice despite the presence of Ube3a in all neurons. These deficits result in excitatory/inhibitory imbalance at cellular and circuit levels and may contribute to seizure susceptibility in AS.     

Overexpression of γ－aminobutyric acid transporter subtype I leads to susceptibility to kainic acid－induced seizure in transgenic mice

Gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter, and the GABAergic synaptic transmission is normally terminated by the rapid uptake through GABA transporters. With transgenic mice ubiquitously overexpressing GABA transporter subtype I (GAT1), the present study explored the pathophysiological role of GAT1 in epileptogenesis. Though displaying no spontaneous seizure activity, these mice exhibit altered electroencephalographic patterns and increased susceptibility to seizure induced by kainic acid. In addition, the GABA(A) receptor and glutamate transporters are up-regulated in transgenic mice, which perhaps reflects a compensatory or corrective change to the elevated level of GAT1. These preliminary findings support the hypothesis that excitatory and inhibitory neurotransmission, and seizure susceptibility can be altered by neurotransmitter transporters.     

Inheritance of Susceptibility to Friend Mouse Leukemia Virus: V. Introduction of a Gene Responsible for Susceptibility in the Genetic Complement of Resistant Mice

Based on the previous observation that a single major autosomal gene controls susceptibility to Friend leukemia virus in mice, an attempt was made to place the gene for susceptibility, Fv(s), from susceptible DDD mice into the genetic complement of resistant C57BL/6 mice. The backcross system was adopted for this purpose, the heterozygotes being selected by progeny test at each generation. During successive backcrosses, the effect of gene Fv(s) was not diluted out, and progeny were almost always obtained as expected from the single-gene hypothesis, with respect to both genotype and phenotype. With the eighth backcross generation, brother-sister mating was done between the heterozygotes, and it produced mice homozygous for gene Fv(s). These susceptible homozygotes and their progeny produced by incross could be assumed congenic with C57BL/6 mice except for susceptibility to Friend leukemia virus. The results indicate that the appearance of early splenomegaly in Friend virus-infected mice is under the control of a single major autosomal gene.     

Comparison of methods for detection of pinworms in mice and rats

Though pinworm infestation remains common in laboratory rodent colonies, there is little information regarding current practices for pinworm detection and their relative efficacy. The authors surveyed research institutions to find out the prevalence of pinworm infestations and the detection methods they used. They also tested mice and rats from colonies that were known to be infested with Syphacia sp. and compared the following detection methods: perianal tape test, fecal flotation, fecal concentration, cecal content examination, cecal flotation and histological examination. Though the different methods yielded comparable efficacy overall, the authors recommend using more than one type of test to increase detection potential.     

Dissociation between the anticonvulsant action of alcohol and its depressant action in mice of different genotypes

The effects of ethanol and pentobarbital on flurothyl seizure susceptibility were studied in two lines of mice that were derived by selective breeding with respect to ethanol sleep time. Short-sleep mice (SS) were more susceptible than long-sleep mice (LS) to flurothyl-induced myoclonus, but there was no line difference in susceptibility to clonus. Low doses of ethanol or pentobarbital increased seizure latencies in both populations, and there was no difference between the lines in the effect of these drugs. The lack of difference in response to ethanol in the two populations indicates that the genetic mechanisms which determine sensitivity to ethanol's anticonvulsant action are not identical with those which determine sensitivity to its depressant action.