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Departments of Veterinary Medicine and Primate Husbandry (KM-R, SR, F-JK) and Virology and Immunology (KDJ), German Primate Center (DPZ), Göttingen, Germany; andDepartment of Virology (HN, SL, EV), Biomedical Primate Research Center, Rijswijk, The Netherlands
| Abstract |
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Key words: Common marmosets; herpesvirus infection; human herpesvirus 1; New World monkeys; stomatitis; vesicoulcerative glossitis.
Nonhuman primates are primary hosts to a number of herpesviruses.3 These viruses generally cause mild or inapparent infections in their natural host, but some are associated with severe disease when transmitted to other species. The well-known spontaneous interspecies transmissibility of herpesviruses is responsible for a high zoonotic risk and may result in fatal diseases of either humans or animals. Human herpesvirus 1 (HHV-1) is one of the best-characterized viruses transmissible from human to nonhuman primates, but spontaneous infections in monkeys appear to be rare. Humans are the original host and the reservoir; they exhibit typical clinical symptoms such as acute gingivostomatitis during the primary infection. In Old World primates, natural HHV-1 infection has been described in gorillas (Gorilla gorilla),7 chimpanzees (Pan troglotydes), bonobos (Pan paniscus),16 and white-handed gibbons (Hylobates lar).6,21,22 In these species, the disease remains localized to mucocutaneous tissues. It seems to be comparable with the human disease and usually does not become a systemic infection. New World monkeys and prosimians are more susceptible to infection and disease. The disease course is severe, leading to death in most cases. In spontaneously infected owl monkeys (Aotus trivirgatus), the generalized febrile disease is characterized by erosions and ulcers of oral mucous membranes and mucocutaneous junctions of the lips, accompanied by focal necrosis and hemorrhages in all organs, including the cerebral cortex. Death occurs within 16 days after the onset of symptoms.14,17 Similar gross lesions are observed in naturally infected tree shrews (Tupaia glis),15 lemurs,12 and most experimentally infected marmoset and tamarin species (Callithrix sp., Saguinus sp.).10 Spontaneous HHV-1 infection was described in a fatal case in black tufted-ear marmosets (Callithrix (C.) penicillata) in a conservation unit of the State park of Serra da Tiririca, Niteroi, in Brazil, as well as in four young pet marmosets (C. jacchus) belonging to private owners in Spain and Brazil.5,11,18
Our report describes a HHV-1 outbreak in a group of C. jacchus housed as a family group after contact with a person who had recrudescent HHV-1 disease. We describe the clinical appearance and pathomorphologic alterations in the disease and virus detection using immunohistologic and molecular techniques as well as virus isolation.
The infected animals belonged to a colony consisting of up to 45 animals kept in a greenhouse or in huts with outdoor facilities. All animals were housed in family groups (breeding couple with up to four generations of offspring). The eight members of the infected family were housed in mesh wire cages in the greenhouse, with both natural daylight and artificial light. The animals were fed a pap in the morning, vegetables, fruits, and animal protein source in the evening, and water ad libitum. In this greenhouse, there were up to 10 different families living without direct contact. Visual contact between family groups was prevented by long curtains, but indirect contact with bodily fluids or other material through caretakers, scientists, and exchanged food or water bowls was possible.
| Clinical Findings |
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-male (marmoset No. 1) showed apathy, anorexia, weakness, and marked salivation in the morning and died the same afternoon. At this time, no other animals in the group showed clinical signs. The following morning one young adult (marmoset No. 2) and the
-female (marmoset No. 3) developed excessive salivation and apathy (Table 1). Closer examination showed ulceration of the lips (Fig. 1) and the oral cavity. All seven animals were treated with Baypamun® (inactivated Parapoxvirus ovis D1701, Bayer, Leverkusen, Germany) 0.5 ml/animal s.c. and 5 mg/kg marbofloxacin Marboxyl® (Vetoquinol, Oberursel, Germany). The next day, the young adult and the female were found dead. All other animals developed the same symptoms and were euthanatized. In summary, all eight animals had a 12 day history of vesicular to ulcerative gingivitis and stomatitis accompanied by severe salivation, serous nasal discharges, anorexia, and depression. Three animals developed lesions covered with fibronecrotic exudate at the mucocutaneous junctions (marmoset Nos. 3, 4, and 7).
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| Pathology |
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Immunohistochemistry for HHV-1 virus was performed on formalin-fixed, paraffin-embedded sections using a monoclonal antibody directed against HHV-1 and -2 antigen (Biogenex, cat No., MU086-UC) at a dilution of 1 : 200, after protease XXIV (Ventana) pretreatment. Immunohistochemistry revealed a specific antigen-antibody reaction in the lingual lesions of all animals (Fig. 4). The whole ulcer region, especially the degenerate epithelial cells, was strongly positive. Furthermore, virus antigen could be detected in the liver and brain tissue of some animals (marmoset Nos. 48). In the liver, virus-positive cells were found within inflammatory cell infiltrates. The central nervous system contained single neurons positive for herpesvirus antigen. The adrenal glands were negative for herpesvirus antigen.
Intranuclear viral nucleocapsids, either empty or filled with electron dense material, were observed by electron microscopy within epithelial cells. Large numbers of enveloped virions in the cytoplasm and intercellular spaces could be demonstrated (Fig. 5). Intranuclear particles measured 80100 nm; the enveloped particles had an outside diameter of 150 mm or more. Many of the virus particles had the hexagonal configuration characteristic of members of the herpesvirus group. Size, location, and morphologic features were consistent with the identification of the virus as a member of the herpesvirus family.
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-herpesviruses. DNA was isolated from infected BHK, Vero, and chimpanzee primary fibroblast cell lines. Viral sequences were amplified by nested polymerase chain reaction (PCR), which is essential for the amplification of primate
-herpesviruses, as described by Black and Eberle.2 A BLAST search in the GenBank, EMBL, DDJB, and PDB sequence databases showed a 99% sequence identity of the PCR fragment with HSV-1 sequences. Furthermore, PCR analysis was performed on several specimens obtained at necropsy and frozen at -80 C. A primer set designated B9/B10 was used to identify the herpesvirus. B9/B10 are located within the highly conserved C1 and C2 regions of the glycoprotein gB encoded by HHV-1, HHV-2, B-virus, SA8, and HVP2 and amplify the highly divergent D2 region of gB (360 bp for HHV-1 [KOS], KO1760, PubMed, genebank). Restriction digestion of the PCR product with HaeIII results in a virus-specific restriction pattern.2
DNA from liver, heart, lung, tongue, lymph node, kidney, spleen, and blood (marmoset No. 2), liver, lymph node, tongue, kidney, spleen, heart, and blood (marmoset No. 5), and liver, lung, spleen, tongue, heart, kidney, and blood (marmoset No. 6) was isolated by using the QIAamp Mini Kit (Quiagen, Hilden, Germany). PCR with DNA from the tongue as template resulted in an amplification product of 360 bp, with that obtained with the HHV-1positive control (Fig. 6). PCR of all other DNA samples did not result in any amplification product. Addition of dimethyl sulfoxide (5%), betaine (1 M), or both did not improve these results. In a gradient PCR with different annealing temperatures ranging from 48 to 60 C, only DNA from the tongue of three animals was positive. Higher annealing temperatures lead to nonspecific bands in all samples. To identify the origin of the PCR amplification products, the purified PCR products were digested with the restriction enzyme HaeIII. As shown in Fig. 7, the restriction fragments had the molecular sizes expected for HHV-1, about 175 bp, 126 bp, and minor bands in the range of 40 and 20 bp (computer predicted).2 They comigrated with the restriction fragments of the HHV-1 control DNA, indicating that the animals were infected with HHV-1.
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It seems likely that close contact with persons suffering from an oral herpesvirus infection was the source of virulent HHV-1. In the case reported here, the animals had contact with a caretaker suffering from a herpes labialislike illness a few days before the outbreak occurred. In most of the reported infections in various nonhuman primates species, it was indicated that contact with humans was the source of infection.6,12,15,17,22 Visitors, students, or caretakers might be able to infect the animals, for example, by passing partly eaten food into the cage. Most reported cases of herpesvirus infection in callithrichids occurred in animals kept by private persons, often in close association with the family. Close contact seems to be necessary for transmission of the infection. The route of transmission in spontaneous infections in nonhuman primates is unknown, but it seems likely that direct contact or aerosol was involved. Once brought into a colony, the disease spread rapidly and had high morbidity and mortality.9 Because humans are the natural or reservoir host for the virus, contact with symptomatically and subclinically HHV-infected humans should always be avoided. Infected persons can excrete the virus even in the absence of visible lesions. The use of appropriate protective clothing and face masks for humans handling nonhuman primates should greatly reduce the risk of infection.
The most characteristic gross findings in the reported cases of HHV-1 infection were discrete vesicles, necrotic plaques, and erosions or ulcers of the oral mucous membranes and mucocutaneous junctions. These lesions cannot be differentiated from herpesvirus T infection, which leads to a systemic infection with identical gross and microscopic lesions.1,9 Herpes tamarinus (HVT) was originally isolated from moribund marmosets (tamarins) and owl monkeys. Squirrel monkeys are the natural host for this virus,13 which is distantly related to the other primate herpesviruses (HHV-1, HHV-2, SA8, and B virus).8,19 A definitive diagnosis can only be made by virus isolation and identification or by immunostaining techniques and molecular investigations as described in this study. Recently, the sequence of the glycoprotein B of squirrel monkey herpesvirus 1 was made public (accession number AYO95366, Breshears et al. 2002). Computer analysis of the primer pair B9/B10 demonstrated the distant relationship of Herpes T to HHV-1. No PCR product could be expected when the animals were infected with Herpes T. Alignments of the primer pair B9/B10 with different computer programs showed no significant homology to the published sequences of HVT. Therefore, the digested PCR products, which were detected in the tongue of three animals, were specific for HHV-1.
In conclusion, callithrichids may represent a highly susceptible host for human-borne herpesvirus infections. The contact with symptomatically and subclinically HHV-infected humans should always be avoided to reduce the risk of infection.
| Acknowledgments |
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| References |
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-herpesviruses by PCR. J Vet Diagn Invest 9:225-231, 1997
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