Antibody response in snakes with boid inclusion body disease.

Boid Inclusion Body Disease (BIBD) is a potentially fatal disease reported in captive boid snakes worldwide that is caused by reptarenavirus infection. Although the detection of intracytoplasmic inclusion bodies (IB) in blood cells serves as the gold standard for the ante mortem diagnosis of BIBD, the mechanisms underlying IB formation and the pathogenesis of BIBD are unknown. Knowledge on the reptile immune system is sparse compared to the mammalian counterpart, and in particular the response towards reptarenavirus infection is practically unknown. Herein, we investigated a breeding collection of 70 Boa constrictor snakes for BIBD, reptarenavirus viraemia, anti-reptarenavirus IgM and IgY antibodies, and population parameters. Using NGS and RT-PCR on pooled blood samples of snakes with and without BIBD, we could identify three different reptarenavirus S segments in the collection. The examination of individual samples by RT-PCR indicated that the presence of University of Giessen virus (UGV)-like S segment strongly correlates with IB formation. We could also demonstrate a negative correlation between BIBD and the presence of anti-UGV NP IgY antibodies. Further evidence of an association between antibody response and BIBD is the finding that the level of anti-reptarenavirus antibodies measured by ELISA was lower in snakes with BIBD. Furthermore, female snakes had a significantly lower body weight when they had BIBD. Taken together our findings suggest that the detection of the UGV-/S6-like S segment and the presence of anti-reptarenavirus IgY antibodies might serve as a prognostic tool for predicting the development of BIBD.

Widespread arenavirus occurrence and seroprevalence in small mammals, Nigeria.

BACKGROUND: Lassa fever, killing thousands of people annually, is the most reported viral zoonotic disease in Nigeria. Recently, different rodent species carrying diverse lineages of the Lassa virus (LASV) in addition to a novel Mobala-like genetic sequence were detected within the country. Here, screening 906 small mammal specimens from 11 localities for IgG antibodies and incorporating previous PCR detection data involving the same populations, we further describe arenavirus prevalence across Nigeria in relation to host species and geographical location. METHODS: Small mammals were trapped during the period 2011-2015 according to geographical location (endemic and non-endemic zones for Lassa fever), season (rainy and dry seasons between 2011 and 2012 for certain localities) and habitat (indoors, peridomestic settings and sylvatic vegetation). Identification of animal specimens from genera such as Mastomys and Mus (Nannomys) was assisted by DNA sequencing. Small mammals were tested for LASV IgG antibody using an indirect immunofluorescence assay (IFA). RESULTS: Small mammals were infected in both the endemic and non-endemic zones for Lassa fever, with a wider range of species IgG-positive (n = 8) than those which had been previously detected to be PCR-positive (n = 3). IgG-positive species, according to number of infected individuals, were Mastomys natalensis (n = 40), Mastomys erythroleucus (n = 15), Praomys daltoni (n = 6), Mus baoulei (n = 5), Rattus rattus (n = 2), Crocidura spp. (n = 2), Mus minutoides (n = 1) and Praomys misonnei (n = 1). Multimammate mice (Mastomys natalensis and M. erythroleucus) were the most ubiquitously infected, with animals testing positive by either PCR or IgG in 7 out of the 11 localities sampled. IgG prevalence in M. natalensis ranged from 1% in Abagboro, 17-36 % in Eguare Egoro, Ekpoma and Ngel Nyaki, up to 52 % in Mayo Ranewo. Prevalence according to locality, season and age was not, however, statistically significant for M. natalensis in Eguare Egoro and Ekpoma, localities that were sampled longitudinally. CONCLUSIONS: Overall, our study demonstrates that arenavirus occurrence is probably more widely distributed geographically and in extent of host taxa than is currently realized. This expanded scope should be taken into consideration in Lassa fever control efforts. Further sampling should also be carried out to isolate and characterize potential arenaviruses present in small mammal populations we found to be seropositive.

Platelets: much more than bricks in a breached wall.

Platelets have various roles in vascular biology and homeostasis. They are the first actor in primary haemostasis and play important roles in thrombosis pathogenesis, but they are also part of innate immunity, which initiates and accelerate many inflammatory conditions. In some contexts, their immune functions are protective, while in others they contribute to adverse inflammatory outcomes. Platelets express numerous receptors and contain hundreds of secretory molecules that are crucial for platelet functional responses. The capacity of platelets to produce and secrete cytokines, chemokines and related molecules, under the control of specific intracellular pathways, is intimately related to their key role in inflammation. They are also able to intervene in tissue regeneration and repair because they produce pro-angiogenic mediators. Due to this characteristic platelets are involved in cancer progression and spreading. In this review we discuss the complex role of platelets, which bridges haemostasis, inflammation and immune response both in physiological and pathological conditions.

Hematopoietic and nonhematopoietic cells promote Type I interferon- and TLR7-dependent monocytosis during low-dose LCMV infection.

Release of inflammatory monocytes from the bone marrow (BM) into the blood is an important physiological response to infection, but the mechanisms regulating this phenomenon during viral infection are not completely defined. Here, we show that low-dose infection with lymphocytic choriomeningitis virus (LCMV) caused rapid, transient inflammatory monocytosis that required type I interferon (IFN) and Toll-like receptor (TLR) 7 signaling. Type I IFN and TLR7 signals were critical for induction of IFN-stimulated gene expression and CCR2 ligand upregulation in the BM microenvironment in response to LCMV infection. Experiments utilizing BM chimeric mice demonstrated that type I IFN and TLR7 signaling on either hematopoietic or nonhematopoietic cells was sufficient to initiate monocytosis in response to LCMV infection. BM plasmacytoid dendritic cells (pDCs) generated type I IFN directly ex vivo, suggesting that pDCs are a hematopoietic contributor of type I IFN in the BM early during LCMV infection. Overall, we describe novel roles for type I IFN and TLR7 signaling in nonhematopoietic cells and BM pDCs in directing IFN-stimulated gene and CCR2 ligand expression in the BM to initiate an increase in blood inflammatory monocytes during viral infection.

Etiología y caracterización epidemiológica del síndrome febril no palúdico en tres municipios del Urabá antioqueño, Colombia / Etiology and epidemiological characterization of non-malarial febrile syndrome in three municipalities of Urabá (Antioquia), Colombia

Introducción. La región de Urabá es endémica para varias enfermedades febriles agudas de origen infeccioso. Sin embargo, solo los pacientes con malaria pueden acceder a un diagnóstico oportuno y rápido, motivo por el cual muchos síndromes febriles no palúdicos quedan sin diagnóstico etiológico claro. Objetivo. Establecer la etiología, describir las manifestaciones clínicas y explorar algunos posibles factores de riesgo relacionados con los síndromes febriles agudos no palúdicos en pacientes procedentes de los municipios de Necoclí, Turbo y Apartadó. Materiales y métodos. Se tomaron muestras de suero en fase aguda y de convalecencia de 220 pacientes febriles negativos para malaria, provenientes de zonas rurales y urbanas de Necoclí, Turbo y Apartadó en los años 2007 y 2008. Se practicaron pruebas para diagnóstico de dengue (detección de anticuerpos IgM por ELISA), leptospirosis (detección de anticuerpos IgM e IgG por IFI), rickettsiosis (detección de anticuerpos IgG por IFI), hantavirus y arenavirus (detección de anticuerpos IgG por ELISA). Resultados. Se encontraron frecuencias de dengue, leptospirosis, rickettsiosis y arenavirus de 37,3 %, 14,1 %, 2,7 % y 0,5 %, respectivamente. Se presentaron 12 casos de coinfección de leptospirosis-dengue y uno de leptospirosis-rickettsiosis-dengue. El sexo masculino y la humedad relativa media, fueron factores de riesgo para dengue. El inicio de signos clínicos en febrero de 2008, se asoció tanto con la infección por dengue como por leptospirosis. Conclusión. Se reafirma la importancia del virus del dengue, Rickettsia spp. y Leptospira spp., como agentes causantes del síndrome febril en la región del Urabá.

Introduction: Urabá, a region on the northern coast of Colombia, is endemic to several acute febrile illnesses of infectious origin; however, only patients with malaria may have access to quick and effective diagnosis. For this reason, many non-malarial febrile patients go without a clear etiologic diagnosis. Aim: To establish the etiology and clinical signs of acute febrile non-malaria syndromes and explore some of the likely risk factors in patients originating in the municipalities of Necocli, Turbo and Apartado who exhibit these symptoms. Materials and methods: We obtained acute and convalescent sera from 220 non-malarial febrile patients from the rural and urban zones of Necocli, Turbo and Apartado during 2007 and 2008. Serologic tests for dengue (IgM by ELISA), leptospirosis (IgM and IgG by IFA), rickettsiosis (IgG by IFI), hanta and arenavirus (IgG by ELISA) were performed. Results: We found that the frequency of infection for dengue, leptospirosis, rickettsiosis and arenavirus, was 37.3%; 14.1%; 2.7% and 0.5%, respectively. There were 12 co-infection cases of leptospirosis-dengue and one of leptospirosis-rickettsiosis-dengue. Male gender and relative humidity were considered risk factors for dengue, and the beginning of clinical signs in February of 2008 was associated with the infection of dengue and leptospirosis. Conclusion: This study confirms previous records that underline the importance of Rickettsia spp, dengue virus and Leptospira spp as causal agents of febrile syndrome in this region of Colombia.

[Etiology and epidemiological characterization of non-malarial febrile syndrome in three municipalities of Urabá (Antioquia), Colombia]. / Etiología y caracterización epidemiológica del síndrome febril no palúdico en tres municipios del Urabá antioqueño, Colombia.

INTRODUCTION: Urabá, a region on the northern coast of Colombia, is endemic to several acute febrile illnesses of infectious origin; however, only patients with malaria may have access to quick and effective diagnosis. For this reason, many non-malarial febrile patients go without a clear etiologic diagnosis. AIM: To establish the etiology and clinical signs of acute febrile non-malaria syndromes and explore some of the likely risk factors in patients originating in the municipalities of Necocli, Turbo and Apartado who exhibit these symptoms. MATERIALS AND METHODS: We obtained acute and convalescent sera from 220 non-malarial febrile patients from the rural and urban zones of Necocli, Turbo and Apartado during 2007 and 2008. Serologic tests for dengue (IgM by ELISA), leptospirosis (IgM and IgG by IFA), rickettsiosis (IgG by IFI), hanta and arenavirus (IgG by ELISA) were performed. RESULTS: We found that the frequency of infection for dengue, leptospirosis, rickettsiosis and arenavirus, was 37.3%; 14.1%; 2.7% and 0.5%, respectively. There were 12 co-infection cases of leptospirosis-dengue and one of leptospirosis-rickettsiosis-dengue. Male gender and relative humidity were considered risk factors for dengue, and the beginning of clinical signs in February of 2008 was associated with the infection of dengue and leptospirosis. CONCLUSION: This study confirms previous records that underline the importance of Rickettsia spp, dengue virus and Leptospira spp as causal agents of febrile syndrome in this region of Colombia.

Presence of Mopeia virus, an African arenavirus, related to biotope and individual rodent host characteristics: implications for virus transmission.

The East African Mopeia virus (MOPV) is an arenavirus closely related to the highly pathogenic West African Lassa virus, even sharing the same reservoir rodent host Mastomys natalensis. Because MOPV is not known to cause human disease, it offers a unique alternative for studying Lassa virus transmission. We investigated how habitat, population density, and host characteristics are related to MOPV occurrence in M. natalensis populations in Morogoro, Tanzania. In 3 contrasting habitats, 511 M. natalensis individuals were trapped, 12.1% (58/480 tested individuals) of which tested seropositive for antibodies and 8.4% (41/489 tested individuals) for MOPV-RNA. Although population densities differ among habitats, density and habitat were not significantly correlated to MOPV-RNA or antibody presence. Antibody presence was not significantly correlated with any host characteristics. In contrast, MOPV-RNA presence was inversely related to weight, age, sexual maturity, and body mass index. The model with body mass index as predictor was the best at predicting infection probability. Thirty-five individuals were exclusively MOPV-RNA positive, 52 were exclusively antibody positive, and 6 were both MOPV-RNA and antibody positive. Interpreting these data using experimental infection results from studies on other arenaviruses, this would mean that these infections were very recent, old, and roughly 1-3 weeks after infection, respectively. The higher RNA prevalence in juveniles implies vertical transmission, or that horizontal transmission occurs mainly in this age group due to lack of immunity, higher susceptibility, and/or higher juvenile contact rates. This study demonstrates the strength of combining information on antibody and RNA presence with host characteristics, and how this information can provide valuable insights into transmission dynamics.

Antibodies to Tacaribe serocomplex viruses (family Arenaviridae, genus Arenavirus) in cricetid rodents from New Mexico, Texas, and Mexico.

Blood samples from 4893 cricetid rodents were tested for antibody (immunoglobulin G) to Whitewater Arroyo virus and Amaparí virus to extend our knowledge of the natural host range and geographical distribution of Tacaribe serocomplex viruses in North America. Antibodies to arenaviruses were found in northern pygmy mice (Baiomys taylori), woodrats (Neotoma spp.), northern grasshopper mice (Onychomys leucogaster), oryzomys (Oryzomys spp.), deermice (Megadontomys nelsoni and Peromyscus spp.), harvest mice (Reithrodontomys spp.), and cotton rats (Sigmodon spp.) captured in New Mexico, Texas, or Mexico. Comparison of endpoint antibody titers to Whitewater Arroyo virus and Amaparí virus in individual blood samples indicated that the Tacaribe complex viruses enzootic in Texas and Mexico are antigenically diverse.

Early and strong immune responses are associated with control of viral replication and recovery in lassa virus-infected cynomolgus monkeys.

Lassa virus causes a hemorrhagic fever endemic in West Africa. The pathogenesis and the immune responses associated with the disease are poorly understood, and no vaccine is available. We followed virological, pathological, and immunological markers associated with fatal and nonfatal Lassa virus infection of cynomolgus monkeys. The clinical picture was characterized by fever, weight loss, depression, and acute respiratory syndrome. Transient thrombocytopenia and lymphopenia, lymphadenopathy, splenomegaly, infiltration of mononuclear cells, and alterations of the liver, lungs, and endothelia were observed. Survivors exhibited fewer lesions and a lower viral load than nonsurvivors. Although all animals developed strong humoral responses, antibodies appeared more rapidly in survivors and were directed against GP(1), GP(2), and NP. Type I interferons were detected early after infection in survivors but only during the terminal stages in fatalities. The mRNAs for CXCL10 (IP-10) and CXCL11 (I-TAC) were abundant in peripheral blood mononuclear cells and lymph nodes from infected animals, but plasma interleukin-6 was detected only in fatalities. In survivors, high activated-monocyte counts were followed by a rise in the total number of circulating monocytes. Activated T lymphocytes circulated in survivors, whereas T-cell activation was low and delayed in fatalities. In vitro stimulation with inactivated Lassa virus induced activation of T lymphocytes from all infected monkeys, but only lymphocytes from survivors proliferated. Thus, early and strong immune responses and control of viral replication were associated with recovery, whereas fatal infection was characterized by major alterations of the blood formula and, in organs, weak immune responses and uncontrolled viral replication.

Restoration of lymphoid organ integrity through the interaction of lymphoid tissue-inducer cells with stroma of the T cell zone.

The generation of lymphoid microenvironments in early life depends on the interaction of lymphoid tissue-inducer cells with stromal lymphoid tissue-organizer cells. Whether this cellular interface stays operational in adult secondary lymphoid organs has remained elusive. We show here that during acute infection with lymphocytic choriomeningitis virus, antiviral cytotoxic T cells destroyed infected T cell zone stromal cells, which led to profound disruption of secondary lymphoid organ integrity. Furthermore, the ability of the host to respond to secondary antigens was lost. Restoration of the lymphoid microanatomy was dependent on the proliferative accumulation of lymphoid tissue-inducer cells in secondary lymphoid organs during the acute phase of infection and lymphotoxin alpha(1)beta(2) signaling. Thus, crosstalk between lymphoid tissue-inducer cells and stromal cells is reactivated in adults to maintain secondary lymphoid organ integrity and thereby contributes to the preservation of immunocompetence.

Clinical laboratory, virologic, and pathologic changes in hamsters experimentally infected with Pirital virus (Arenaviridae): a rodent model of Lassa fever.

The clinical laboratory, virologic, and pathologic changes occurring in hamsters after infection with Pirital virus (Arenaviridae) are described. Pirital virus infection in the hamsters was characterized by high titered viremia, leukocytosis, coagulopathy, pulmonary hemorrhage and edema, hepatocellular and splenic necrosis, and marked elevation of serum transaminase levels. All of the animals died within 9 days. The clinical and histopathological findings in the Pirital virus-infected hamsters were very similar to those reported in severe human cases of Lassa fever, suggesting that this new animal model could serve as a low-cost and relatively safe alternative for studying the pathogenesis and therapy of Lassa fever.

Differential tissue-specific regulation of antiviral CD8+ T-cell immune responses during chronic viral infection.

The hallmarks of the immune response to viral infections are the expansion of antigen-specific CD8(+) cytotoxic T lymphocytes (CTLs) after they encounter antigen-presenting cells in the lymphoid tissues and their subsequent redistribution to nonlymphoid tissues to deal with the pathogen. Control mechanisms exist within CTL activation pathways to prevent inappropriate CTL responses against disseminating infections with a broad distribution of pathogen in host tissues. This is demonstrated during overwhelming infection with the noncytolytic murine lymphocytic choriomeningitis virus, in which clonal exhaustion (anergy and/or deletion) of CTLs prevents immune-mediated pathology but allows persistence of the virus. The mechanism by which the immune system determines whether or not to mount a full response to such infections is unknown. Here we present data showing that the initial encounter of specific CTLs with infected cells in lymphoid tissues is critical for this decision. Whether the course of the viral infection is acute or persistent for life primarily depends on the degree and kinetics of CTL exhaustion in infected lymphoid tissues. Virus-driven CTL expansion in lymphoid tissues resulted in the migration of large quantities of CTLs to nonlymphoid tissues, where they persisted at stable levels. Surprisingly, although virus-specific CTLs were rapidly clonally exhausted in lymphoid tissues under conditions of chronic infection, a substantial number of them migrated to nonlymphoid tissues, where they retained an effector phenotype for a long time. However, these cells were unable to control the infection and progressively lost their antiviral capacities (cytotoxicity and cytokine secretion) in a hierarchical manner before their eventual physical elimination. These results illustrate the differential tissue-specific regulation of antiviral T-cell responses during chronic infections and may help us to understand the dynamic relationship between antigen and T-cell populations in many persistent infections in humans.

Endothelial cell function alteration after Junin virus infection.

Hematologic involvement is the main feature of Argentine hemorrhagic fever (AHF), an endemo-epidemic disease caused by Junin virus (JV). Since endothelial dysfunction could play a role in AHF-altered hemostasis, we studied human umbilical vein endothelial cell (HUVEC) infection with a virulent (JVv) and a non-virulent (JVa) JV strain. Cells were infected by the two JV variants with no detectable apoptosis or cytopathic effect. Both viral variants up-regulated ICAM-1 and VCAM-1 levels, while von Willebrand factor (VWF) production was decreased. Prostacyclin (PGI2) release and decay accelerating factor (DAF) expression were greater in JVv- than in JVa-infected or control cells. Furthermore, nitric oxide (NO) production and endothelial nitric oxide synthase (eNOS) expression was only raised in JVv-infected supernatants. Significant NO and PGI2 values were also detected in AHF patient sera. These data demonstrate that endothelial cell responses are triggered subsequently by JV infection, suggesting that such alterations play a major role in the pathogenesis of AHF and perhaps in other viral-induced hemorrhagic diseases.

Evaluation of an enzyme-linked immunosorbent assay for detection of antibodies to Junin virus in rodents.

Junin virus is the etiological agent of Argentine hemorrhagic fever, a serious rodent-borne disease. An enzyme-linked immunosorbent assay (ELISA) to detect Junin virus IgG antibodies in rodents was evaluated using sera from 27 Calomys musculinus and five Calomys laucha, inoculated experimentally with a live attenuated strain of this arenavirus. The test performance was compared against an indirect immunofluorescence assay (IFA). The ELISA had a sensitivity and specificity of 100% and a reproducibility of 87.9% for samples with titers above the selected cut-off value. IFA had lower sensitivity (53%) with the same specificity. The ELISA results were similar, whether carried out on whole blood or serum samples, thus eliminating the need for serum separation. A high correlation (K=0.86) between ELISA and IFA results was obtained from 1011 wild sigmodontine and murine rodents collected within and outside of the Argentine hemorrhagic fever endemic area. These results indicate that Junin virus IgG ELISA is the most suitable assay for detection of Junin virus antibodies in rodent samples.

Experimental infection of Neotoma albigula (Muridae) with Whitewater Arroyo virus (Arenaviridae).

The Whitewater Arroyo virus (WWA) is a newly described North American arenavirus. The purpose of this study was to elucidate the biology of this virus in its natural rodent host, Neotoma albigula (white-throated woodrat). Thirteen adult, 7 juvenile, and 8 newborn woodrats each were inoculated subcutaneously with 1,000 cell culture infectious dose50 of the WWA virus prototype strain AV 9310135. All 28 animals became infected (as measured by the recovery of infectious virus and/or seroconversion) and no overt illness was associated with infection. Infection and virus shedding in the adult animals were transient (less than 59 days) whereas virus shedding in animals inoculated at birth persisted through 164 days of age. These results indicate that the duration of WWA virus infection in N. albigula is dependent upon the animal's age at the onset of infection and that neonatal infection can result in chronic (perhaps lifelong) virus shedding.

Clinical case definitions for Argentine hemorrhagic fever.

Argentine hemorrhagic fever (AHF) is a potentially lethal infection in Argentina. The case-fatality ratio is >15%, but treatment reduces the mortality rate to <1%. Diagnosis is based on clinical and laboratory criteria, but no case definition has been validated. A chart review was conducted for patients hospitalized with suspected AHF. Individuals with a fourfold rise in antibody titer were classified as cases. The combination of a platelet count of <100,000/mm3 and a white blood cell (WBC) count of <2,500/mm3 had a sensitivity and specificity of 87% and 88%, respectively, thus suggesting that the use of these criteria in a case definition would be helpful for epidemiological studies of AHF. The combination of a platelet count of <100,000/mm3 and a WBC count of <4,000/mm3 had a sensitivity of 100% and a specificity of 71%; the use of these criteria in a case definition should be helpful for screening patients for therapy with immune plasma in the region where AHF is endemic.

Incidencia de la infección por virus pirital en roedores de la especie sigmodón alstoni: efectos de la infección sobre la especie / Incidence of the pirital virus infection in rodents of the sigmodon alstony species: effects of the infection on the specie

El virus Pirital es un nuevo arenavirus descubierto en Venezuela, sin embargo no existen evidencias de que pueda ser un virus patógeno para el humano. Sus efectos en el roedor que le sirve de reservorio natural: sigmodón alstoni se analiza en el presente estudio. Un total de 478 roedores: S. alstoni fueron capturados entre junio de 1994 a diciembre de 1995 en el Municipio Papelón, estado Portuguesa. Se recolectaron muestras de sangre y bazo para el aislamineto e identificación de virus en cultivo de células Vero E6. La densidad de la población de roedores S. alstoni mostró un patrón estacional con un máximo éxito de trampeo al final de la estación de sequía (Marzo-Abril). Esta variación temporal no estuvo correlacionada con variaciones en la prevalencia de infección por virus Pirital. El promedio de infección en la especie fue de 33,8 por ciento con un incremento no significativo en la prevalencia de infección entre animales juveniles y adultos. El efecto de la infección por el virus Pirital en el peso y tamaño del cuerpo de los roedores así como en la fertilidad, número de animales por camada, etc. no fue significativamente diferente cuando se compararon los animales infectados con los no infectados

Experimental reproduction of severe hypoglycemia and spiking mortality syndrome using field-derived and embryo-passaged preparations.

The clinical signs, enteritis, weight depression, and hypoglycemia of spiking mortality syndrome were experimentally reproduced in broiler breeders and broiler chicks. Inocula included 1) virus-like particles from intestines of chicks with spiking mortality syndrome that had been banded in a discontinuous Renograffin gradient, 2) homogenized darkling beetles collected from litter of farms where spiking mortality syndrome had occurred repeatedly, and 3) homogenized embryos which had been inoculated with the Renograffin-banded material. Arkansas variant infectious bronchitis virus and arenavirus-like particles were identified in the inocula. Serology on samples from surviving chicks suggested the presence of an avian encephalomyelitis virus in one of the inocula. One-day-old (n = 172) and 2.5-day-old (n = 30) chicks were inoculated orally, and some were also injected intraperitoneally or subcutaneously, with 0.5 ml of the inocula. Twelve to fourteen days postinoculation, chicks were fasted for 4-6 hours, then briefly stressed with a cool water spray. Within 1.5 hours, inoculated chicks began dying with severe hypoglycemia and clinical signs of spiking mortality syndrome. Body weights were significantly depressed. Uninoculated controls (n = 130) from the same hatches, also fasted and stressed, were unaffected clinically and were not hypoglycemic. One group (n = 52) of inoculated chicks exposed to a controlled lighting program was unaffected clinically, had significantly higher mean plasma glucose levels, and had significantly less body weight depression than chicks exposed to continuous lighting. We concluded that exposure to controlled amounts of light/darkness can ameliorate much of the hypoglycemia, mortality, and runting-stunting associated with spiking mortality syndrome of chickens. The significance of the viruses and virus-like particles detected in the inocula is currently under investigation.

Pathogenesis of Pichinde virus infection in strain 13 guinea pigs: an immunocytochemical, virologic, and clinical chemistry study.

Pichinde virus has been adapted to produce lethal infection of Strain 13 guinea pigs. Viral replication and presence of viral antigen in frozen tissues stained by immunofluorescence has been previously described. Further investigation into the pathogenesis of this disease has been hampered by the lack of a light microscopic method for correlating histologic lesions and the presence of Pichinde viral antigens. For this purpose, we developed a sensitive immunocytochemical technique for staining Pichinde viral antigens in formalin-fixed, paraffin-embedded tissue. Enhancement of the immunocytochemical staining with nickel chloride markedly improved detection of viral antigens. We examined frozen and formalin-fixed tissues from Strain 13 guinea pigs for viral antigens by light microscopy and immunocytochemistry at various intervals after infection with Pichinde virus. Progressive involvement of different tissues correlated with organ injury measured by serum biochemical abnormalities. Pichinde viral antigen was first detected in splenic macrophages five days after infection and their subsequent destruction facilitated persistent viremia. The inability to clear virus led to multiple organ infection and vascular involvement. Ensuing infections involved particularly the liver, spleen, adrenal glands, lungs, and intestines. Gastroenteritis developed, with extensive involvement of the muscularis mucosa throughout the gastrointestinal tract. Water and food intake decreased rapidly after day 8, leading to marked weight loss. Fatty changes of the liver suggested metabolic derangement that was further exacerbated terminally by adrenal infection and pulmonary impairment.