Non-Human Primate Models of Orthopoxvirus Infections

Clinical Manifestations of an Outbreak of Monkeypox Virus in Captive Chimpanzees in Cameroon, 2016

Monkeypox virus (MPXV) is a reemerging virus of global concern. An outbreak of clade I MPXV affected 20 captive chimpanzees in Cameroon in 2016. We describe the epidemiology, virology, phylogenetics, and clinical progression of this outbreak. Clinical signs included exanthema, facial swelling, perilaryngeal swelling, and eschar. Mpox can be lethal in captive chimpanzees, with death likely resulting from respiratory complications. We advise avoiding anesthesia in animals with respiratory signs to reduce the likelihood of death. This outbreak presented a risk to animal care staff. There is a need for increased awareness and a One Health approach to preparation for outbreaks in wildlife rescue centers in primate range states where MPXV occurs. Control measures should include quarantining affected animals, limiting human contacts, surveillance of humans and animals, use of personal protective equipment, and regular decontamination of enclosures.

The changing epidemiology of monkeypox and preventive measures: an update

Monkeypox is a systemic exanthematous viral disease presenting with fever, lymphadenopathy, and vesicular rash. The zoonotic virus causing this disease is endemic to many sub-Saharan African countries, where a steady rise in cases has been witnessed for the past 30 years. However, monkeypox re-emerged as the largest outbreak of the West African clade (clade II) of monkeypox virus in Nigeria in 2017. This poxvirus received only minimal global attention until recently, when cases emerged in Europe and rapidly spread globally in certain sections of the community, such as men having sex with men or bisexuals, with human-to-human transmission. Monkeypox virus has established its presence in humans, crossing geographical boundaries, and clusters of infections may occur among individuals in close contact. All six WHO regions have reported monkeypox cases without any epidemiological association with endemic regions. The ongoing multicountry outbreak suggests that silent human-to-human transmission has been happening in Europe and the United States for a while. For containment of the outbreak, active surveillance and rapid identification of new cases are essential. The availability of vaccines is currently limited. Policymakers must focus on awareness programmes, primary preventive or post-exposure vaccination, and treatment with antivirals to control the ongoing outbreak.

Clinical manifestations of human monkeypox infection and implications for outbreak strategy

Monkeypox is an orthopoxvirus-based zoonotic illness that causes symptoms similar to smallpox in humans. Health care workers around the world are making it a priority to educate themselves on the many clinical manifestations and treatment options for this virus as public health agencies strive to stop the current outbreak. The infected do not have access to any treatment at this time. However, information obtained from the smallpox pandemic has led researchers to examine vaccinia immune globulin (IVG), tecovirimat, and cidofovir as viable treatments for monkeypox. Moreover, medication like tecovirimat may be given in extreme circumstances, and supportive therapy can help with symptom relief. The European Medicines Agency (EMA) certified tecovirimat as safe and effective against monkeypox in 2022, per the World Health Organization (WHO). As there are now no established guidelines for alleviating these symptoms, the efficacy of these treatments is highly questionable. Some high-profile cases in recent years have cast doubt on the long-held belief that this illness is rare and always resolves itself without treatment. We aimed to conduct this review to get a deeper comprehension of the evolving epidemiology of monkeypox by analysing such factors as the number of confirmed, probable, and potential cases, the median age at presentation, the mortality rate, and the geographic distribution of the disease. This study offers an updated review of monkeypox and the clinical treatments that are currently available as a result of the worldwide epidemics.

Monkeypox: Some Keys to Understand This Emerging Disease

In 1958, several monkeys in a Copenhagen laboratory developed a skin rash from which an orthopoxvirus could be isolated, which was named monkeypox virus (MPXV). However, the natural animal reservoir for MPXV is thought to be a rodent. The first human case occurred in 1970, and the incidence has increased progressively throughout the years. Starting May 2022, the number of cases outside Africa has soared, especially in Western Europe. There are two clades of MPXV, Congo Basin, with higher virulence and mortality, and Western Africa (WA). MPXV from the present outbreak has been proposed to be classified as Clade 3, distinct from the WA clade by at least 50 substitutions, which may increase human-to-human transmissibility. Most cases correspond to men in their 30s who have sex with men, and the possibility of sexual transmission is under investigation. Though there is no evidence of human-to-animal transmission, pets of positive human cases may be classified as low risk, including dogs, cats, and birds, who can be quarantined at home, and high risk, such as pet rabbits or mice, who should be isolated in official laboratories for observation. The current epidemiological data do not support the risk of a pandemic.

Dynamics of Pathological and Virological Findings During Experimental Calpox Virus Infection of Common Marmosets (Callithrix jacchus)

Experimental intranasal infection of marmosets (Callithrix jacchus) with calpox virus results in fatal disease. Route and dose used for viral inoculation of the test animals mimics the natural transmission of smallpox, thus representing a suitable model to study pathogenesis and to evaluate new vaccines against orthopoxvirus infection. However, the pathogenic mechanisms leading to death are still unclear. Therefore, our study aimed at investigating the kinetics of pathological alterations to clarify the pathogenesis in calpox virus infection. Following intranasal inoculation with two different viral doses, common marmosets were sacrificed on days 3, 5, 7, 10 and 12 post inoculation. Collected tissue was screened using histopathology, immunohistochemistry, transmission electron microscopy, and virological assays. Our data suggest that primary replication took place in nasal and bronchial epithelia followed by secondary replication in submandibular lymph nodes and spleen. Parallel to viremia at day 7, virus was detectable in many organs, mainly located in epithelial cells and macrophages, as well as in endothelial cells. Based on the onset of clinical signs, the histological and ultrastructural lesions and the immunohistochemical distribution pattern of the virus, the incubation period was defined to last 11 days, which resembles human smallpox. In conclusion, the data indicate that the calpox model is highly suitable for studying orthopoxvirus-induced disease.

Limited susceptibility of rhesus macaques to a cowpox virus isolated from a lethal outbreak among New World monkeys

This study was undertaken to investigate the susceptibility of rhesus monkeys to the calpox virus, an orthopoxvirus (OPXV) of the Cowpox virus species (CPXV), which is uniformly lethal in common marmosets. Six rhesus monkeys were either intravenously (i.v.) or intranasally (i.n.) exposed to the virus. Monitoring of the macaques after viral exposure included physical examinations, the determination of viral load by real-time PCR and plaque assay, and the analysis of humoral responses. Two i.v. inoculated animals developed numerous classical pox lesions that started after inoculation at days 7 and 10. Both animals became viremic and seroconverted. They exhibited maximal numbers of lesions of approximately 50 and 140 by day 21. One animal completely recovered, while the other one suffered from a phlegmonous inflammation of a leg initially induced by a secondarily infected pox lesion and was euthanized for animal welfare reasons. In contrast to previous pathogenicity studies with the calpox virus in marmosets, none of the four animals inoculated intranasally with doses of the calpox virus exceeding those used in marmosets by orders of magnitude showed typical clinical symptoms. No viral DNA was detectable in the blood of those animals, but three animals seroconverted. In two of these three animals, infectious virus was sporadically isolated from saliva. This indicates that rhesus monkeys are less susceptible to calpox virus infection, which limits their use in further intervention studies with OPXV.

From the working group "Experimental Pathology" to the department "Pathology Unit" – historical development in retrospect

Abstract. The Pathology Unit of the German Primate Center started as the working group of Experimental Pathology in 1992. This small group with one veterinary pathologist and a technician was founded based on an idea of Prof. Dr. Kuhn, who wanted to strengthen the pathology research activities and to establish a centralized electron microscopy laboratory. Later on, experimental pathology, veterinary services and primate husbandry were integrated as the Department of Veterinary Medicine and Primate Husbandry but subsequently again separated. Prof. Dr. Franz-Josef Kaup, the head of the previously integrated department, remained in his capacity as the leader of the different units. Over the years, the research activities have changed from SIV-associated pathology to other infectious diseases. Today, the main research focus is on the pathogenesis of orthopoxvirus infection, primate pathology, neglected tropical diseases and nonhuman primates as models for chronic respiratory diseases. This paper gives an overview of the historical development and aspects of research activities.