Infected Pups Research Articles

Development of a heterologous model in germfree suckling rats for studies of rotavirus diarrhea.

Germfree suckling rats were infected with an SA11 rotavirus strain. Infected pups developed diarrhea associated with histopathological changes. The virus was detected in feces and in the small intestine. Cellular vacuolation was observed in the villi of the jejunum. These results provide a new model for further investigations of group A rotavirus infection.

Immune abnormalities in guinea pigs with asymptomatic congenital syphilis.

Spleens from 1-20-wk-old guinea pigs infected in utero with Treponema pallidum and age-matched controls, born to normal and heat-killed (56 degrees C, 2 h.) T. pallidum-injected mothers, were examined for their in vitro lymphoproliferative response to phytohemagglutinin, concanavalin A, and lipopolysaccharide. Additionally, T cell surface markers (mu-chain, pan T, CD4, and CD8) were determined in spleen, lymph node, and peripheral blood from 10-wk infected and normal pups by single and dual parameter fluorescence-activated cell sorter analysis. Compared with control animals, congenitally infected animals showed a remarkable prolonged naive-type of immune response as reflected by the higher (p < 0.01) proliferative responses to both T cell mitogens (up to 20 wk of age), and the weaker response to the B cell mitogen, significantly different (p < 0.01) at 10 wk of age. As opposed to controls, in all organs examined the level of CD8+ (cytotoxic/suppressor) T cells was significantly diminished (p < 0.01); consequently, the CD4/CD8 ratio was significantly elevated (p < 0.05). The role of C4 complement component and the nature and potential role of the immature T and B lymphocyte responses in asymptomatic congenital syphilis is discussed.

Uncinariasis in northern fur seal and California sea lion pups from California.

Northern fur seal (Callorhinus ursinus) (n = 25) and California sea lion (Zalophus californianus) (n = 53) pups, found dead on rookeries on San Miguel Island (California, USA), were examined for adult Uncinaria spp. Prevalence of these nematodes was 96% in fur seal pups and 100% in sea lion pups. Mean intensity of Uncinaria spp. per infected pup was 643 in fur seals and 1,284 in sea lions. Eggs of Uncinaria spp. from dead sea lion pups underwent embryonation in an incubator; development to the free-living third stage larva occurred within the egg. This study provided some specific information on hookworm infections in northern fur seal and California sea lion pups on San Miguel Island. High prevalence rate of Uncinaria spp. in both species of pinnipeds was documented and much higher numbers (2X) of hookworms were present in sea lion than fur seal pups.

Vertical Transmission of Neospora caninum in Mice

Herein we report a murine model to examine transplacental transmission, transmammary transmission, or both, of Neospora caninum. Prevalence of transplacental transmission in outbred Swiss-Webster mouse pups was 85%, with 11 of 13 litters containing at least 1 transplacentally infected pup. Sixty-two percent of litters born to experimentally infected dams contained 85% or more transplacentally infected pups. Numbers of pups congenitally infected per litter was higher if dams were inoculated during the first half of pregnancy. Transplacental transmission decreased to 25% when a singly infected dam delivered a second litter. Transmammary transmission was observed in 1 of 51 pups suckling dams experimentally infected 5, 10, or 15 days postparturition. No pups were infected when cross-fostered onto chronically infected dams.

Comparison of the efficacies of three heartworm preventives against experimentally induced infections with Ancylostoma caninum and Toxocara canis in pups

Summary Forty 11- to 12-week-old helminth-naive Beagles were categorized by sex and weight and randomly assigned to 4 treatment groups (group 1, ivermectin/ pyrantel pamoate; group 2, milbemycin oxime; group 3, untreated control; group 4, diethylcarbamazine/ oxibendazole). Each pup was inoculated po with approximately 100 infective Ancylostoma caninum larvae and 100 larvated Toxocara canis eggs on day 0, and repeatedly at 7-day intervals thereafter until day 56. Administration of anthelmintics also began on day 0, and subsequent treatments were administered according to label recommendations at 30-day intervals (groups 1 and 2) or daily (group 4) for a period of 90 consecutive days. Body weight and A caninum and T canis fecal egg counts were measured at weekly intervals, and clinical observations of health status were conducted twice daily. Pups were euthanatized on day 90, and total gastrointestinal worm burdens were determined. Compared with the mean A caninum egg counts of group-3 control pups, egg counts in group-1 pups were significantly (P ≤ 0.0001) lower on every sampling date from day 28 to 90, egg counts of group-2 pups were significantly (P ≤ 0.0001) lower on sampling days 35, 42, 49, 63, 70, 77, and 84, and were consistently the highest of all treated groups, and egg counts of group-4 pups were significantly (P ≤ 0.0001) lower on every sampling date from day 14 to day 90, and were consistently the lowest of all treated groups. Compared with mean A caninum egg counts of group-3 pups, egg counts in group-1 and group-2 pups were lower by 97.8 and 90.8%, respectively. Numbers of adult hookworms recovered at necropsy were significantly (P ≤ 0.05) lower by 99.4, 83.9, and 99.9% in groups 1, 2, and 4, respectively. Patent T canis infections were detected in 11 of 40 pups and only 5 adult worms were recovered from 4 pups at necropsy. These findings were attributed to age resistance to T canis by maturing pups rather than to a primary pharmacologic effect. This study identified substantial differences in the quantities of hookworm eggs in experimentally infected pups receiving ivermectin/pyrantel, milbemycin oxime, or diethylcarbamazine/oxibendazole at label dosages, but the observed performance of all products was consistent with their respective label indications.

Vertical Transmission of Neospora caninum in Dogs

Herein we report a murine model to examine transplacental transmission, transmammary transmission, or both, of Neospora caninum. Prevalence of transplacental transmission in outbred Swiss-Webster mouse pups was 85%, with 11 of 13 litters containing at least 1 transplacentally infected pup. Sixty-two percent of litters born to experimentally infected dams contained 85% or more transplacentally infected pups. Numbers of pups congenitally infected per litter was higher if dams were inoculated during the first half of pregnancy. Transplacental transmission decreased to 25% when a singly infected dam delivered a second litter. Transmammary transmission was observed in 1 of 51 pups suckling dams experimentally infected 5, 10, or 15 days postparturition. No pups were infected when cross-fostered onto chronically infected dams.

Gamma camera scintigraphy for direct visualization of larval migration in Strongyloides stercoralis-infected dogs.

Gamma camera scintigraphy of dogs infected with radiolabeled third-stage larvae of Strongyloides stercoralis was successful for visualizing larval migration in a live host. Ten-day-old pups were infected subcutaneously in a lateral inguinal site with 100,000 75Se-selenomethionine-labeled third-stage S. stercoralis and imaged serially using a clinical gamma camera during the prepatent period. Radioactivity corresponding to the larval inoculum was visualized at the infection site immediately after injection. Radioactivity spread diffusely, corresponding to radial dispersal of larvae from the infection site. The majority of the radioactivity concentrated over or through the abdomen from 48 to 144 hr after infection. Larvae arrived in the small intestine in numbers adequate for visualization beginning at 114 hr after infection. At no time was there concentration of radioactivity associated with the lungs of an infected pup. A control pup injected only with 75Se-selenomethionine showed uniform activity diffusely throughout the entire body at all times. We concluded that the majority of larvae moved to the gut by means other than the pulmonary route.

Minute virus of canines (MVC, canine parvovirus type-1): pathogenicity for pups and seroprevalence estimate.

Minute virus of canines (MVC, canine parvovirus type-1) caused inapparent to severe illness in neonatal specific-pathogen-free pups exposed by the oronasal route. The experimental disease was generally mild. Four of 21 infected pups had clinical signs of respiratory illness, but only 2 pups, not euthanized during the early postinoculation period, developed severe illness or died. Principal pathologic changes included bronchitis and interstitial pneumonia with various degrees of lymphadenitis. In contrast to the reported field cases, enteric signs were absent in the experimentally infected animals. Histopathologic changes in the small intestine were mild or absent. Bronchial, bronchiolar, and alveolar epithelial cells appeared to be the sites of initial and most extensive viral growth, reflecting the pattern of histopathologic changes. The disease caused by MVC was mild in comparison to that caused by canine parvovirus-type 2. MVC now appears to be established as a cause of illness in young pups and of transplacental infections with embryo resorption. The prevalence of MVC hemagglutination-inhibiting antibodies was high (approximately 50%) in adult dog sera from widely separated geographic areas of the United States.

Glycans as targets for monoclonal antibodies that protect rats against Trichinella spiralis.

We have investigated the role of glycans on Trichinella spiralis antigens in recognition by rat monoclonal antibodies (mAbs) which protect rat pups against challenge with the parasite. In pups born to infected dams or pups passively immunized with mAbs, antibodies eliminate a challenge dose from the intestine within hours ('rapid expulsion'). Because such dramatic protection can be afforded by mAbs, we have sought to characterize the parasite antigens they target. In this report we show that protective antibodies were unable to bind excretory/secretory (ES) antigens deglycosylated with trifluoromethanesulphonic acid (TFMS). In addition, oligosaccharides isolated from glycoproteins by alkaline hydrolysis or peptide: N glycosidase F (PNGase F) digestion were bound by protective, but not non-protective, mAbs. Glycans affinity purified with protective mAb 9D bound to all but one protective mAb. These antibodies have been shown previously to bind to the surfaces of intact larvae, indicating that the glycan is exposed on the parasite surface. Candidate glycans that may be involved in binding protective mAbs have unusual tri- and tetra-antennary structures with terminal tyvelose moieties (Reason et al., Glycobiology, 4, 000-000, 1994). Coating of the larval surface with such glycans may serve to protect the parasite and its secreted products from enzymatic attack as the parasite travels to and resides in its epithelial niche.

Maternal Administration of Granulocyte Colony-Stimulating Factor Improves Neonatal Rat Survival After a Lethal Group B Streptococcal Infection

Abstract Maternally administered recombinant human granulocyte colony- stimulating factor (rhG-CSF) has been shown to cross the placenta and induce a peripheral neutrophilia and increases in the marrow and spleen neutrophil storage pools in fetal and newborn rats. In the present study, we have used this model system to investigate the efficacy of prenatally administered rhG-CSF on neonatal defense to a lethal challenge with Group B-beta hemolytic Streptococcus (GBS). Pregnant rats were injected with rhG-CSF twice daily beginning 6 days before parturition. At birth, all pups were infected with a dose of GBS that is lethal for 90% of infected pups (LD90). Survival was monitored daily for 5 days. Survival of infected pups from saline-treated mothers beyond 60 hours after infection was 10%. No difference in survival was observed among pups from mothers treated 2 and 4 days before parturition. In contrast, we determined that survival was 82.5% among infected pups from mothers treated for 6 days before parturition with rhG-CSF. Our results demonstrate that maternal administration of rhG- CSF augments neonatal defenses against a lethal bacterial challenge.

Maternal administration of granulocyte colony-stimulating factor improves neonatal rat survival after a lethal group B streptococcal infection

Maternally administered recombinant human granulocyte colony-stimulating factor (rhG-CSF) has been shown to cross the placenta and induce a peripheral neutrophilia and increases in the marrow and spleen neutrophil storage pools in fetal and newborn rats. In the present study, we have used this model system to investigate the efficacy of prenatally administered rhG-CSF on neonatal defense to a lethal challenge with Group B-beta hemolytic Streptococcus (GBS). Pregnant rats were injected with rhG-CSF twice daily beginning 6 days before parturition. At birth, all pups were infected with a dose of GBS that is lethal for 90% of infected pups (LD90). Survival was monitored daily for 5 days. Survival of infected pups from saline-treated mothers beyond 60 hours after infection was 10%. No difference in survival was observed among pups from mothers treated 2 and 4 days before parturition. In contrast, we determined that survival was 82.5% among infected pups from mothers treated for 6 days before parturition with rhG-CSF. Our results demonstrate that maternal administration of rhG-CSF augments neonatal defenses against a lethal bacterial challenge.

Impact of experimental genital mycoplasmosis on pregnancy outcome in Sprague-Dawley rats

Specific-pathogen-free (SPF) female Sprague-Dawley rats were infected by intravaginal inoculation with 3 x 10(7) CFU of Mycoplasma pulmonis X1048 in 0.1 ml of Frey's broth or with an equal volume of sterile Frey's broth. A minimum of 10 days postinfection, rats were bred to noninfected males. Rats were necropsied at days 11, 14, and 18 of gestation and within 24 h of parturition. Throughout pregnancy, at least 50% of rats remained infected in the lower genital tract. At parturition, the major site of colonization was the respiratory tract (P = 0.02). M. pulmonis was not isolated from any site of any control rat. Pregnancy outcome was adversely affected by infection with M. pulmonis. Infected rats had significantly smaller litter sizes at day 18 of gestation (P < or = 0.01) and at term (P < or = 0.004). No statistically significant differences among the gestational stages in infected rats were noted for litter size. Total litter weight is a reflection of individual pup weight and of the number of pups born. Therefore, it was obvious that infected rats would have a significantly lower (P < or = 0.008) total litter weight than noninfected controls. However, when individual pup weights were considered, infected pups (n = 49) also had significantly lower (P < or = 0.0001) birth weights than did noninfected controls (n = 68). The incidence of an adverse pregnancy outcome at term (stillbirths, macerated fetuses, or resorptions) was higher (P < or = 0.01) in infected rats than in noninfected control rats. No stillborn pups or macerated fetuses were observed in any control term rats (n = 5). All control rats had live-born pups. Three infected rats had no live-born offspring. Resorptions were more common in infected rats than in control rats (P < or = 0.01). The mean number of resorptions per rat was greater in rats which went to term than in rats necropsied during gestation, indicating that the severity of disease was progressive. The rat is frequently the laboratory animal of choice for a wide variety of reproductive studies, and the experimental parameters that are most often measured (litter size, pup weight, and neonatal survival) were all adversely affected by genital mycoplasmosis. Genital mycoplasmosis is important as an animal model for the interaction of infectious agents and the host during pregnancy as well as in its own right as a confounding variable affecting research projects which use the rat as a model to study reproductive function and physiology.

Neonatal mouse model of group B streptococcal infection.

Neonatal mice were infected with type III group B streptococcal (GBS) strain M781 by the intraperitoneal route. Age-related susceptibility to challenge was seen within the first 5 days of life. Quantitative blood cultures demonstrated a rapid increase in bacterial numbers during the first 30 h after challenge. Infected pups showed clinical signs of septicemia, and most succumbed within 48 h of challenge. Histopathologic evaluation of the neonates showed bacterial infection within 1 day after challenge. Pregnant adult mice were given a single inoculation of serum raised in rabbits against a tetanus toxoid-conjugated type III GBS polysaccharide vaccine. This serum passively protected 100% of the offspring. This neonatal mouse model of GBS infection and protection may be suitable for study of various forms of intervention.

Rat model of congenital toxoplasmosis

A rat model of congenital toxoplasmosis is described for the study of protective immunity and chemotherapy during pregnancy. Six Sprague-Dawley 7- to 15-day gestational rats were inoculated orally (three rats, trial A) or subcutaneously (three rats, trial B) with 10,000 infective oocysts of the CT-1 strain of Toxoplasma gondii. The tissues of rat pups born from these rats were bioassayed for T. gondii infection. T. gondii was recovered from 30 of 33 (90.9%, trial B) and 23 of 28 (82.17%, trial A) rat pups bioassayed at 1 to 134 days of age. Two 10- to 14-day gestational pregnant rats were inoculated subcutaneously (trial C) with 10,000 infective bradyzoites from tissue cysts; 10 of 23 (43.8%) of the newborn pups were infected with T. gondii. Congenital infection occurred only when rats were infected during pregnancy. None of three rats in trial A that had given birth to congenitally infected rat pups produced congenitally infected rat pups during the second pregnancy.

The pathology of subclinical infection of encephalitozoon cuniculi in canine dams producing pups with overt encephalitozoonosis

The macroscopic, microscopic and clinical pathology and the serology of 2 clinically normal Staffordshire Bull Terrier bitches, both of whom produced pups with confirmed encephalitozoonosis, is described. Mild histopathological changes, similar to those seen in the infected pups, were observed. The spores of Encephalitozoon cuniculi were seen in the renal tubules of the kidney of one of the bitches. The serum urea concentrations of one of the bitches was elevated. A positive titre against E. cuniculi was obtained in both of the bitches. A 10-year-old girl who had had close contact with one of the infected litters of pups, seroconverted to E. cuniculi. Her two siblings were serologically negative.

Experimental transmission of a granulocytic form of the tribe Ehrlichieae by Dermacentor variabilis and Amblyomma americanum to dogs

Summary Transstadial transmission of granulocytic Ehrlichieae in dogs was attempted using ticks, Amblyomma americanum and Dermacentor variabilis. Ticks were exposed by feeding as nymphs on acutely infected pups; adult ticks then fed to repletion on susceptible adult dogs that were monitored daily for signs of infection. Evidence of transmission was not observed in control dogs or in those exposed to D variabilis. In contrast, dogs exposed to A americanum developed serologic or clinical evidence of infection, but organisms were not seen in blood smears until corticosteroids were administered, causing recrudescence and accompanying parasitemia. At 12 days after subinoculation of blood obtained from donor adult dogs, before corticosteroids were administered, a febrile response, thrombocytopenia, and appearance of morulae in neutrophilic granulocytes were observed in 2 susceptible recipient dogs.

Evaluation of the efficacy of an epsiprantel/pyrantel combination against gastrointestinal helminths of dogs

ABSTRACTTrials were conducted to evaluate the anthelmintic effect of a combination of epsiprantel at a dose rate of 5‐5 mg/kg bodyweight and pyrantel pamoate at 5 mg pyrantel base/kg against Toxocara canis in prenatally infected unweaned greyhound pups, Toxascaris leonina, Uncinaria stenocephala, Trichuris vulpis and Dipylidium caninum in naturally infected adolescent greyhounds and Ancylostoma caninum, U stenocephala. Taenia hydatigena and Taenia pisiformis in artificially infected laboratory beagles. The product was well accepted and produced no obvious side effects. Percentage efficacy values based on post mortem worm counts were: T hydatigena 100; T pisiformis 100; D caninum 100; adult T canis 84‐0; adult T leonina 96‐5; immature T leonina 99‐8; U stenocephala 99‐0 and 87‐7; A caninum 92‐7; and T vulpis 43‐3.

Maternal cell‐mediated cytolysis of CMV‐infected fetal cells and the outcome of pregnancy in the guinea pig

Cytolytic recognition of CMV-infected syngeneic fetal guinea pig cells by maternal peripheral blood mononuclear cells (PBMC) was suppressed late in pregnancies of uninfected guinea pig breeders with less than 25% conceptus loss. A small subset of less successful uninfected pregnancies with greater than or equal to 50% fetal wastage exhibited only partial suppression of cytolytic activity against CMV-infected fetal cells. Primary CMV infection of dams extending into early pregnancy induced augmented cytolysis of CMV-infected fetal cells, but not MA104 NK cell targets, throughout gestation and resulted in 70% loss of conceptus. Decreased suppression of cytolytic activity against CMV-infected fetal cells in uninfected pregnancy was also associated with runting of newborn pups, which was not as severe as that observed in congenitally CMV-exposed or CMV-infected pups. Congenitally infected pups were affected more than their exposed but uninfected litter mates. Lack of suppression of cytolysis of CMV-infected syngeneic fetal cells, whether spontaneous or CMV-infection-induced, appears to be associated with poor pregnancy outcome.

Indirect fluorescent antibody test for the detection of antibodies to Echinoccus granulosus in experimentally infected pups

Adult parasites of Echinococcus granulosus of buffalo origin were used as antigen in the indirect fluorescent antibody test (IFA) for detection of antibodies to E. granulosus in experimentally infected pups. The technique permitted detection of antibodies on Day 5 post-infection (p.i.) and up to Day 80 p.i. in infected animals. The antigen-antibody reaction was characterized by the appearance of a specific brilliant greenish yellow fluorescence on the embryophore of mature eggs present within and outside the gravid segment of the cestode. A maximum antibody titre of 1:320 at Day 50 p.i. was observed in the infected pups, coinciding with maturation of adult worms in the intestine of the host.

MECHANIHMB OF INTESTINAL IMMUNITY TO ROTAVIRUS ENTERITIS: CHARACTERISTICS OF PERSISTENT INFECTION IN SEVERE COMBINED IMMUNODEFICIENT (SCID) MICE

Using ELISA and fluorescent antibody assays, we followed shedding and replication of mouse rotavirus (MRV) in groups of suckling, adult, and lactating female SCID, and age matched normal (control) mice. The mice were infected, with orally administered live MRV, or spontaneously via ingestion of virus containing feces from infected pups. Suckling normal and SCID mice were infected with MRV with development of disease in a predictable manner. However, SCID infants exhibited more severe disease and persistent viral shedding in the feces. Although normal adult mice could not be infected with the virus, SCID adults developed infection in about 5-10% of villous enterocytes, but with little or no clinical disease, significantly, these animals continued to shed virus in feces intermittently 4 to 5 months (to date) after primary infection. No MRV specific secretory antibody activity was induced in the intestine in SCID mice. However, such infected adults manifested significant resistance to subsequent attempts at reinfection with high dose of virus (8×105 ID50) administered orally. The virus recovered from the SCID mice was highly infectious when re-inoculated in susceptible suckling animals. These data suggest that the virus and host may have achieved a “steady state” in the gut in immunodeficient animals, implying that factors other than rotavirus-specific serum and secretory antibody or T cell function are important in controlling virus replication in the gut.