Does post acute care reduce the mortality of octogenarian and nonagenarian patients undergoing hip fracture surgery?

BACKGROUND: With the increasing number of elderly individuals worldwide, a greater number of people aged 80 years and older sustain fragility fracture due to osteopenia and osteoporosis. METHODS: This retrospective study included 158 older adults, with a median age of 85 (range: 80-99) years, who sustained hip fragility fracture and who underwent surgery. The patients were divided into two groups, one including patients who joined the post-acute care (PAC) program after surgery and another comprising patients who did not. The mortality, complication, comorbidity, re-fracture, secondary fracture, and readmission rates and functional status (based on the Barthel index score, numerical rating scale score, and Harris Hip Scale score) between the two groups were compared. RESULTS: The patients who presented with fragility hip fracture and who joined the PAC rehabilitation program after the surgery had a lower rate of mortality, readmission rate, fracture (re-fracture and secondary fracture), and complications associated with fragility fracture, such as urinary tract infection, cerebrovascular accident, and pneumonia (acute coronary syndrome, out-of-hospital cardiac arrest, or in-hospital cardiac arrest. CONCLUSIONS: PAC is associated with a lower rate of mortality and complications such as urinary tract infection, bed sore, and pneumonia in octogenarian and nonagenarian patients with hip fragility fracture.

Prenatal exposure to low-dose di-(2-ethylhexyl) phthalate (DEHP) induces potentially hepatic lipid accumulation and fibrotic changes in rat offspring.

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer that is widely used to enhance the flexibility and durability of various products. As an endocrine disruptor, DEHP can interfere with normal hormonal functions, posing substantial health risks to organisms. Given the critical role of the liver in DEHP metabolism, we investigated potential liver damage in offspring induced by prenatal exposure to low doses of DEHP in Sprague Dawley rats. Pregnant rats were divided into three groups and administered 20 or 200 µg/kg/day of DEHP or corn oil vehicle control via oral gavage from gestation days 0-20. Male rat offspring were euthanized on postnatal day 84, and blood and liver specimens were collected for analysis. We observed fibrotic changes in the livers of the exposed groups, accompanied by the proliferation and activation of hepatic stellate cells and upregulated expression of TGF-B and collagen 1A1. Additionally, an inflammatory response, characterized by increased macrophage infiltration and elevated levels of pro-inflammatory cytokines, was evident. Third, hepatic and serum triglyceride and serum cholesterol were notably increased, along with upregulated expression of lipid metabolism-related proteins, such as sterol regulatory element-binding protein-1c, acetyl-CoA carboxylase, fatty acid synthase, and diacylglycerol O-acyltransferase 1, particularly in the low-dose group. These results suggest that prenatal exposure to DEHP can disrupt lipid metabolism, resulting in hepatic lipid accumulation in the offspring. This exposure may also induce an inflammatory response that contributes to the development of liver fibrosis. Thus, even at relatively low doses, such exposure can precipitate latent liver damage in offspring.

Protobothrops jerdonii (Jerdon's pit viper) and Protobothrops himalayanus (Himalayan lance-headed pit viper) bites: Clinical report on envenomings from North-East India, managed through remote consultation by a national-level Poison control center.

Members of the genus Protobothrops are amongst the more than twenty-eight range-restricted Indian pit viper species. Their bites and envenomings are rarely documented from India. Pit viper envenomings can be challenging to treat in the Indian setting, since available antivenoms do not satisfactorily neutralize their venoms. Herein, we present the first Indian reports on bites and envenoming by Protobothrops jerdonii and Protobothrops himalayanus resulting in local effects, coagulopathy and acute kidney injury in the case of the former and possible mild, isolated coagulopathy in the case of the latter; and discuss management-related challenges in the context of absent specific antivenoms.

Comparative analysis of Deinagkistrodon acutus venom from Taiwan and China utilizing chromatographic, electrophoretic, and bioinformatic approaches, along with ELISA employing a monospecific antivenom.

Deinagkistrodon acutus is a medically important pitviper inhabiting mainly South China and Taiwan. The hemorrhagic effects of its envenoming are compatible to its venom, which is abundant in metalloproteases (svMPs) and C-type lectin-like proteins. In this study, we investigated geographic variations in the venom of D. acutus collected from Taiwan and four Mainland Chinese provinces: Fujian, Jiangxi, Anhui, and Hunan. The variations were assessed through high-performance liquid chromatography, non-metric multidimensional scaling analysis, gel electrophoresis, and enzyme-linked immunosorbent assay (ELISA) with a monospecific antivenom (DaMAV) generated against the Taiwanese D. acutus venom, and discussed based on venom-protein sequences in databases and literature related to D. acutus venom. Additionally, the cross-reactivity of DaMAV against Crotalus horridus and Calloselasma rhodostoma venoms was investigated. We noted differential abundances of D. acutus venom metalloproteases, C-type lectin-like proteins, and phospholipase A2, along with point mutations and selective expression of serine protease isoforms. The ELISA results revealed that the venom from Taiwan was more reactive toward Taiwanese DaMAV than the four Mainland Chinese venoms, consistent with chromatographic profile differences, whereas C. horridus venom presented moderate cross-reactivity with DaMAV. The observed immunoreactivities of these venom with DaMAV can be attributed to the high prevalence of their PIII-svMPs, which are the dominant antigens, and the conservation of PIII-svMP epitopes.

In vitro immunoreactivity and in vivo neutralization of Trimeresurus gracilis venom with antivenoms targeting four pit viper species.

Snakebite envenomation is a significant global health issue that requires specific antivenom treatments. In Taiwan, available antivenoms target a variety of snakes, but none specifically target Trimeresurus gracilis, an endemic and protected species found in the high mountain areas of Taiwan. This study evaluated the effectiveness of existing antivenoms against T. gracilis venom, focusing on a bivalent antivenom developed for Trimeresurus stejnegeri and Protobothrops mucrosquamatus (TsPmAV), as well as monovalent antivenoms for Deinagkistrodon acutus (DaAV) and Gloydius brevicaudus (GbAV). Our research involved in vivo toxicity testing in mice and in vitro immunobinding experiments using (chaotropic) enzyme-linked immunosorbent assays, comparing venoms from four pit viper species (T. gracilis, T. stejnegeri, P. mucrosquamatus, and D. acutus) with three types of antivenoms. These findings indicate that TsPmAV partially neutralized T. gracilis venom, marginally surpassing the efficacy of DaAV. In vitro tests revealed that GbAV displayed higher binding capacities toward T. gracilis venom than TsPmAV or DaAV. Comparisons of electrophoretic profiles also reveal that T. gracilis venom has fewer snake venom C-type lectin like proteins than D. acutus, and has more P-I snake venom metalloproteases or fewer phospholipase A2 than G. brevicaudus, T. stejnegeri, or P. mucrosquamatus. This study highlights the need for antivenoms that specifically target T. gracilis, as current treatments using TsPmAV show limited effectiveness in neutralizing local effects in patients. These findings provide crucial insights into clinical treatment protocols and contribute to the understanding of the evolutionary adaptation of snake venom, aiding in the development of more effective antivenoms for human health.

Characterization of chicken-derived antibody against Alpha-Enolase of Streptococcus pneumoniae.

Streptococcus pneumoniae is a clinically relevant pathogen notorious for causing pneumonia, meningitis, and otitis media in immunocompromised patients. Currently, antibiotic therapy is the most efficient treatment for fighting pneumococcal infections. However, an arise in antimicrobial resistance in S. pneumoniae has become a serious health issue globally. To resolve the problem, alternative and cost-effective strategies, such as monoclonal antibody-based targeted therapy, are needed for combating bacterial infection. S. pneumoniae alpha-enolase (spEno1), which is thought to be a great target, is a surface protein that binds and converts human plasminogen to plasmin, leading to accelerated bacterial infections. We first purified recombinant spEno1 protein for chicken immunization to generate specific IgY antibodies. We next constructed two single-chain variable fragments (scFv) antibody libraries by phage display technology, containing 7.2 × 107 and 4.8 × 107 transformants. After bio-panning, ten scFv antibodies were obtained, and their binding activities to spEno1 were evaluated on ELISA, Western blot and IFA. The epitopes of spEno1 were identified by these scFv antibodies, which binding affinities were determined by competitive ELISA. Moreover, inhibition assay displayed that the scFv antibodies effectively inhibit the binding between spEno1 and human plasminogen. Overall, the results suggested that these scFv antibodies have the potential to serve as an immunotherapeutic drug against S. pneumoniae infections.

Spotted Temporal Lobe Necrosis following Concurrent Chemoradiation Therapy Using Image-Guided Radiotherapy for Nasopharyngeal Carcinoma.

Background: To explore spotted temporal lobe necrosis (TLN) and changes in brain magnetic resonance imaging (MRI) after image-guided radiotherapy (IGRT) in a patient with nasopharyngeal carcinoma (NPC). Case presentation: a 57-year-old male was diagnosed with stage III NPC, cT1N2M0, in 2017. He underwent concurrent chemoradiation therapy (CCRT) with cisplatin (30 mg/m2) and 5- fluorouracil (5-FU, 500 mg/m2) plus IGRT with 70 Gy in 35 fractions for 7 weeks. The following MRI showed a complete response in the NPC. However, the patient suffered from fainting periodically when standing up approximately 3 years after CCRT. Neck sonography showed mild atherosclerosis (< 15%) of bilateral carotid bifurcations and bilateral small-diameter vertebral arteries, with reduced flow volume. The following MRI showed a 9 mm × 7 mm enhancing lesion in the right temporal lobe without locoregional recurrence, and TLN was diagnosed. The lesion was near the watershed area between the anterior temporal and temporo-occipital arteries. The volume of the necrotic lesion was 0.51 c.c., and the mean dose and Dmax of the lesion were 64.4 Gy and 73.7 Gy, respectively. Additionally, the mean dose, V45, D1 c.c. (dose to 1 ml of the temporal lobe volume), D0.5 c.c. and Dmax of the right and left temporal lobes were 11.1 Gy and 11.4 Gy, 8.5 c.c. and 6.7 c.c., 70.1 Gy and 67.1 Gy, 72.0 Gy and 68.8 Gy, and 74.2 Gy and 72.1 Gy, respectively. Conclusion: Spotted TLN in patients with NPC treated by IGRT may be difficult to diagnose due to a lack of clinical symptoms and radiological signs. Endothelial damage may occur in carotid and vertebral arteries within the irradiated area, affecting the small branches supplying the temporal lobe and inducing spotted TLN. Future research on the relationship between vessels and RT or CCRT and the development of TLN is warranted.

Thirteen-month duration of immunity of an oral canine vaccine against challenge with Bordetella bronchiseptica.

BACKGROUND: Very few studies have evaluated the duration of immunity of Bordetella bronchiseptica vaccines in dogs, and to date, no studies have been published on the duration of immunity of oral canine Bordetella bronchiseptica vaccines. This study was designed to determine the effectiveness of a single dose of an oral B bronchiseptica vaccine in dogs when challenged 13 months after vaccination. METHODS: Two groups of approximately eight-week-old beagles were vaccinated once with 1 ml of placebo vaccine (oral, n=17) or 1 ml of Recombitek Oral Bordetella (oral, n=17). Thirteen months after vaccination, both groups were challenged with virulent B bronchiseptica via aerosolisation. RESULTS: Thirteen of 17 dogs in the placebo group (76.5 per cent) and no dogs in the Recombitek Oral Bordetella vaccine group (0.0 per cent) developed spontaneous cough of two or more consecutive days (disease case definition). Dogs in the Recombitek Oral Bordetella group had a significantly lower prevalence of disease with prevented fraction of 1 (100 per cent prevention). In addition, the number of days coughing, duration of cough and prevalence of tracheal and nasal shedding were significantly lower for dogs vaccinated with Recombitek Oral Bordetella. CONCLUSIONS: The study demonstrated that vaccination with Recombitek Oral Bordetella is effective in preventing disease and reducing shedding 13 months after vaccination when compared with dogs vaccinated with a placebo.

Stability of Bovine viral diarrhea virus antigen in ear punch samples collected from bovine fetuses.

Fourteen first-calf heifers were tested free of antibodies against Bovine viral diarrhea viruses (BVDV) by serum neutralization and free of BVDV by polymerase chain reaction. Twelve were exposed to BVDV-1b strain CA0401186a at 84-86 days of gestation, and 2 were exposed to mock inoculum and served as negative controls. Fetuses were harvested by cesarean section at 115-117 days of gestation. The 12 fetuses removed from the BVDV-exposed heifers were BVDV positive based on virus isolation from kidney, thymus, cerebellum, and spleen. It can be assumed that these fetuses would have developed into persistently infected calves had they been allowed to go to term. Virus was not isolated from the fetuses of control animals. Ear punch samples were collected from all fetuses at time of harvest. Antigen capture enzyme-linked immunosorbent assay (ACE), using a commercial kit, was performed on ear punch samples that were frozen within 5 hr of collection and stored at -20 degrees C until tested, tested after storage for 7 days at room temperature (18-25 degrees C), or tested after storage for 7 days at 37 degrees C. Samples stored for 7 days at room temperature or 37 degrees C lost an average of 34% of their starting weight. All samples from BVDV isolation-positive fetuses tested positive by ACE, whereas samples from nonexposed fetuses tested negative, regardless of storage conditions. These results suggest that ACE testing of skin samples collected from aborted fetuses and stillborn calves found in the field may represent a practical surveillance method for BVDV-induced reproductive disease.

Comparative onset of immunity of oral and intranasal vaccines against challenge with Bordetella bronchiseptica.

Three groups of approximately eight-week-old beagles were vaccinated once with 1 ml of placebo vaccine (oral, n=9), 1 ml of Recombitek® Oral Bordetella (oral, n=10) or 1 ml Nobivac® Intra-Trac3 (intranasal, 0.5 ml/nostril, n=10). Seven days after vaccination, the three groups were challenged with virulent Bordetella bronchiseptica via aerosolisation. Eight of nine dogs in the placebo group and no dogs in the Recombitek® Oral Bordetella or Nobivac® Intra-Trac3 vaccine groups developed spontaneous cough of two or more consecutive days (disease case definition). Dogs in the Recombitek® Oral Bordetella and Nobivac® Intra-Trac3 groups had a significantly lower incidence of disease (P<0.0001) with a 100 per cent preventable fraction. The study demonstrated that vaccination with either Recombitek® Oral Bordetella or Nobivac® Intra-Trac3 is effective in preventing disease seven days after vaccination when compared with dogs vaccinated with a placebo.

Rabies vaccination in dogs using a dissolving microneedle patch.

Because humans get rabies primarily through dog bites, stray dog population control and mass or mandatory vaccination of domestic dogs and other animals has virtually eliminated human rabies in industrialized countries. However, thousands of people in developing countries die of rabies each year due to the inability to control dog populations and implement mass vaccination because of financial, logistical and other challenges. The availability of an easier-to-administer and more cost-effective vaccine may help to address some of these issues. Here, we propose the use of dissolving microneedle patches for simple and potentially cost-effective rabies vaccination, and assess the safety and immunogenicity of microneedle patch vaccination using a rabies DNA vaccine in dogs. The vaccine was stable upon formulation and storage for at least 3weeks at 4°C in a microneedle patch. For vaccination, the patches were applied to the inner ear by hand without an applicator. Microneedle patches were well tolerated in the skin, with mild erythema, minimal wheal formation and complete resolution of skin reactions within 7days, and generated no systemic adverse events. Microneedle patches were at least as immunogenic as intramuscular injection at the same dose, as demonstrated by similar serum neutralizing antibody titers. A ten-fold lower vaccine dose administered by microneedle patch generated a weaker immune response compared to full-dose intramuscular vaccination. We conclude that dissolving microneedle patches may provide an innovative approach to mass vaccination of dogs.

Evaluation of immune responses in horses immunized using a killed Sarcocystis neurona vaccine.

Clinically normal horses developed cellular immunity to Sarcocystis neurona following IM vaccination with a commercial killed S. neurona vaccine, as indicated by the development of measurable anti-S. neurona IgG antibodies and additional intradermal skin testing. Large-scale independent assessments of the vaccine's performance and safety are in progress under field conditions. The next step in the evaluation of this vaccine would be to attempt experimental challenge after a reproducible reliable equine model of S. neurona encephalitis has been established that allows for reisolation of the pathogen after challenge.

Stability of Bovine viral diarrhea virus 1 nucleic acid in fetal bovine samples stored under different conditions.

Infection of pregnant cattle with both species of Bovine viral diarrhea virus (BVDV) can result in reproductive disease that includes fetal reabsorption, mummification, abortion, stillbirths, congenital defects affecting structural, neural, reproductive, and immune systems, and the birth of calves persistently infected with BVDV. Accurate diagnosis of BVDV-associated reproductive disease is important to control BVDV at the production unit level and assessment of the cost of BVDV infections in support of BVDV control programs. The purpose of the current study was to examine the stability of viral nucleic acid in fetal tissues exposed to different conditions, as measured by detection by polymerase chain reaction. Five different types of fetal tissue, including brain, skin and muscle, ear, and 2 different pooled organ samples, were subjected to conditions that mimicked those that might exist for samples collected after abortions in production settings or possible storage conditions after collection and prior to testing. In addition, tissues were archived for 36 months at -20°C and then retested, to mimic conditions that might occur in the case of retrospective surveillance studies. Brain tissue showed the highest stability under the conditions tested. The impact of fecal contamination was increased following archiving in all tissue types suggesting that, for long-term storage, effort should be made to reduce environmental contaminants before archiving.

Strain impact on equine herpesvirus type 1 (EHV-1) abortion models: viral loads in fetal and placental tissues and foals.

Equine herpesvirus-1 (EHV-1) continues to cause both sporadic and epidemic abortions despite extensive vaccination. Lack of progress in the development of protective vaccines may be hindered by the lack of equine abortion models that employ contemporary EHV-1 strains. The objective of our experiments was to compare a contemporary EHV-1 strain with a previously described challenge strain, and to quantify EHV-1 loads in various maternal and fetal tissues. Infection experiments were performed in two groups of 7 pregnant pony mares at 270-290 days of gestation with a contemporary EHV-1 strain (University of Findlay 2003 isolate - OH03) or an EHV-1 strain isolated over 30 years ago, and previously described in abortion models (Ab4). All mares in both groups exhibited nasal viral shedding and viremia. Infection with OH03 resulted in 1/7 abortion and infection with Ab4 resulted in 5/7 abortions. In the OH03 challenge, placentas of foals delivered at term showed little detectable virus, while the aborted fetus expressed high levels of virus infection in the spleen and liver, lower levels in the lung and thymus, and lowest levels in the chorioallantois. After Ab4 challenge, high viral loads were detected in fetal and placental tissues in abortions. In the two normal deliveries, the chorioallantois contained virus levels comparable with the chorioallantois of aborted foals and both foals shed EHV-1 starting on day 4 of life, but were clinically healthy. Our results demonstrate the continued importance of strain selection for abortion models, and this study is the first report of viral load quantification using contemporary methods. Extremely high EHV-1 loads in decidua from abortions illustrate the infection risk posed to other horses.

Cell-mediated immunity evaluation in foals infected with virulent equine herpesvirus-1 by multi-parameter flow cytometry.

The cell-mediated immune (CMI) response of foals to virulent equine herpesvirus-1 (EHV-1) infection was evaluated by multi-parameter flow cytometry (FCM). Ten 7-8-month-old EHV-1 seronegative foals were infected intranasally with virulent EHV-1 and 10 foals served as uninfected controls. Blood samples were collected 6 and 7 weeks after infection to test for specific CMI responses to live heterologous EHV-1 recall antigen. The activation markers included major histocompatibility complex class II (MHC II), intracellular interferon gamma (IFN-gamma) and interleukin 4 (IL-4). The results from both tests were averaged before statistical analysis. Following EHV-1 stimulation, the MHC II expression index (EI) increased significantly in CD2+CD4+CD8- and CD2+CD4-CD8+ subsets of the infected group. At 4 days after incubation, the non-antigen stimulated CD2+CD4-CD8- subset of the infected group expressed a high percentage (61.1%) of MHC II. When stimulated with EHV-1, the MHC II expression declined significantly but remained at a relatively high percentage (34.4%). The IFN-gamma EI was significantly higher in infected foals in all major T cell subsets (CD2+) while only the CD2+CD4+CD8- subset showed a significant increase in intracellular IL-4 EI. The FCM results showed strong specific CMI responses to EHV-1 by all three tested parameters compared to the control group (p<0.01). The high MHC II expression in the CD2+CD4-CD8- subset suggests that this T cell subset may represent a gammadelta TCR repertoire and thereby plays an important role as antigen presenting cells in the horse, as reported in other species. Being able to simultaneously quantify the frequency of specific lymphocyte subsets and the expression of cytokines that characterize activation of lymphocytes and protective CMI by multi-parameter FCM enables evaluation of subset-specific CMI responses to EHV-1 infection. This system can be applied to measure CMI responses to other equine vaccines and pathogens.

Extra-cellular signal-regulated kinase 1/2 (ERK1/2) activated in the hippocampal CA1 neurons is critical for retrieval of auditory trace fear memory.

The brain regions involved with trace fear conditioning (TFC) and delayed fear conditioning (DFC) are well-characterized, but little is known about the cellular representation subsuming these types of classical conditioning. Previous evidence has shown that activation of the amygdala is required for both TFC and DFC, while TFC also involves the hippocampus for forming conditioned response to tone. Lesions of the hippocampus did not affect tone learning in DFC, but it impaired learning in TFC. Synaptic plasticity in the hippocampus, underlying a cellular representation subsuming learning and memory, is in part modulated by extra-cellular signal-regulated kinase (ERK) signaling pathway. ERK1/2 activation is required for both TFC and DFC during memory formation, but whether this pathway is involved in memory retrieval of TFC is still unknown. In the present study, we investigated changes in ERK1/2 phosphorylation after memory retrieval in groups of mice that received TFC, DFC, tone-shock un-paired conditioning, and naïve control. Our results showed that ERK1/2 phosphorylation was elevated in the hippocampal CA1 region after retrieval of all conditioned fear responses. In particular, in the TFC group, immunohistochemistry indicated higher level of ERK1/2 phosphorylation in the hippocampal pyramidal neurons 30min after tone testing. Inhibition of the ERK1/2 signaling pathway diminished fear memory elicited by a tone in TFC. Together these results suggest that the memory retrieval process in TFC is more dependent on ERK1/2 signaling pathway than that in DFC. ERK1/2 signaling is critical for retrieval associative memory of temporally noncontiguous stimuli.

Evaluation of the cell-mediated immune response to reduced doses of Mycobacterium avium ssp. paratuberculosis vaccine in cattle.

Vaccination against Johne's disease with an inactivated, oil-adjuvanted Mycobacterium avium ssp. paratuberculosis (MAP) bacterin can reduce clinical signs in infected herds; however, the development of indurated swelling at the injection site limits vaccine acceptability to producers. This study determined whether a reduced dose of vaccine antigen, with a full dose of adjuvant, would produce comparable T cell-mediated immune responses with smaller lesions. T cell responses induced by in vitro stimulation with MAP antigen from calves vaccinated with full, half, and quarter doses of antigen were evaluated 2, 4, and 9 months after vaccination by multi-parameter flow cytometry (FCM) and the whole blood interferon-gamma (WB IFN-gamma) assay. The WB IFN-gamma responses were significantly elevated in vaccinated animals, but did not differ significantly between doses. FCM demonstrated antigen-specific responses for both IFN-gamma and IL-4 in the CD4 T cell population from vaccinated animals, while CD8 T cells and gammadelta T cells mainly responded with increased IFN-gamma. Dose may have affected some T cell subset parameters at some time points, but intradermal skin test responses, WB IFN-gamma production, IFN-gamma responses by T cell subsets in FCM were not significantly different between full, half, or quarter doses of antigen. Injection site lesions were smaller in animals vaccinated with a lower dose of antigen, but reached statistical significance (P<0.05) in the half dose group only.

Pro-inflammatory and antiviral cytokine expression in vaccinated and unvaccinated horses exposed to equine influenza virus.

Most studies of the cytokine response to influenza virus infection have been carried out in human, porcine and murine models, however the data available on equine cytokines is limited. An experimental challenge study was undertaken in unvaccinated naïve horses and horses vaccinated with a commercial inactivated influenza vaccine. The humoral antibody response to vaccination and virus challenge was measured by single radial haemolysis (SRH) assay and clinical signs of influenza and viral shedding were monitored post-challenge. Levels of three equine pro-inflammatory cytokines interleukin (IL)-1beta, IL-6 and tumor necrosis factor (TNF)-alpha and the antiviral cytokine interferon (IFN)-alpha were examined by quantitative RT-PCR of mRNA. Vaccination provided significant clinical and virological protection and resulted in a significant reduction of IFN-alpha and IL-6 expression on day 2 post-challenge. The patterns of cytokine expression observed in control animals suffering from influenza after challenge are comparable to those reported in studies of other species.