Canine parvovirus infection in housed raccoon dogs and foxes in Finland

Changes in Mass Treatment of the Canine Parvovirus ICU Population in Relation to Public Policy Changes during the COVID-19 Pandemic

Previous work has indicated that canine parvovirus (CPV) prevalence in the Central Texas region may follow yearly, periodic patterns. The peak in CPV infection rates occurs during the summer months of May and June, marking a distinct “CPV season”. We hypothesized that human activity contributes to these seasonal changes in CPV infections. The COVID-19 pandemic resulted in drastic changes in human behavior which happened to synchronize with the CPV season in Central Texas, providing a unique opportunity with which to assess whether these society-level behavioral changes result in appreciable changes in CPV patient populations in the largest CPV treatment facility in Texas. In this work, we examine the population of CPV-infected patients at a large, dedicated CPV treatment clinic in Texas (having treated more than 5000 CPV-positive dogs in the last decade) and demonstrate that societal–behavioral changes due to COVID-19 were associated with a drastic reduction in CPV infections. This reduction occurred precisely when CPV season would typically begin, during the period immediately following state-wide “reopening” of business and facilities, resulting in a change in the typical CPV season when compared with previous years. These results provide evidence that changes in human activity may, in some way, contribute to changes in rates of CPV infection in the Central Texas region.

Host-specific parvovirus evolution in nature is recapitulated by in vitro adaptation to different carnivore species

Canine parvovirus (CPV) emerged as a new pandemic pathogen of dogs in the 1970s and is closely related to feline panleukopenia virus (FPV), a parvovirus of cats and related carnivores. Although both viruses have wide host ranges, analysis of viral sequences recovered from different wild carnivore species, as shown here, demonstrated that >95% were derived from CPV-like viruses, suggesting that CPV is dominant in sylvatic cycles. Many viral sequences showed host-specific mutations in their capsid proteins, which were often close to sites known to control binding to the transferrin receptor (TfR), the host receptor for these carnivore parvoviruses, and which exhibited frequent parallel evolution. To further examine the process of host adaptation, we passaged parvoviruses with alternative backgrounds in cells from different carnivore hosts. Specific mutations were selected in several viruses and these differed depending on both the background of the virus and the host cells in which they were passaged. Strikingly, these in vitro mutations recapitulated many specific changes seen in viruses from natural populations, strongly suggesting they are host adaptive, and which were shown to result in fitness advantages over their parental virus. Comparison of the sequences of the transferrin receptors of the different carnivore species demonstrated that many mutations occurred in and around the apical domain where the virus binds, indicating that viral variants were likely selected through their fit to receptor structures. Some of the viruses accumulated high levels of variation upon passage in alternative hosts, while others could infect multiple different hosts with no or only a few additional mutations. Overall, these studies demonstrate that the evolutionary history of a virus, including how long it has been circulating and in which hosts, as well as its phylogenetic background, has a profound effect on determining viral host range.

Canine parvovirus (CPV) is an important example of a viral pathogen that evolved by cross-species transmission and mutation to initiate a disease pandemic. Carnivore parvoviruses infect many species, and their passage in different hosts may select mutations that facilitate host jumping; for example, natural passage of CPV in raccoons may have facilitated its adaptation to dogs. Conversely, some raccoon-adapted viruses are non-infectious to dogs, illustrating that host range barriers exist among different carnivores. Here we demonstrate that these barriers can be overcome by only a few mutations in the virus that likely alter host receptor binding, and that host adaptation can differ dramatically among very similar viruses. Importantly, we also show that passage of viruses in cell cultures of different hosts results in mutations at the same sites that vary in nature and confer fitness increases, strongly suggesting that they are adaptively important. These findings demonstrate that parvoviruses may cross species barriers to infect less susceptible hosts through single or only a few mutations, and that differences in the genetic background, host range, and/or evolutionary history of the viruses influence their propensity to jump hosts. Overall, these discoveries help reveal the mechanisms that control host switching and viral emergence.

Frequent cross-species transmission of parvoviruses among diverse carnivore hosts

Although parvoviruses are commonly described in domestic carnivores, little is known about their biodiversity in nondomestic species. A phylogenetic analysis of VP2 gene sequences from puma, coyote, gray wolf, bobcat, raccoon, and striped skunk revealed two major groups related to either feline panleukopenia virus ("FPV-like") or canine parvovirus ("CPV-like"). Cross-species transmission was commonplace, with multiple introductions into each host species but, with the exception of raccoons, relatively little evidence for onward transmission in nondomestic species.

Distemper vaccination of farmed fur animals in Finland

The most important farmed fur animal species in Finland are the American mink (Mustela vison), blue fox (Alopex lagopus), silver fox (Vulpes vulpes) and raccoon dog (Nyctereutes procyonoides); all are susceptible to canine distemper. The only distemper vaccines currently available are for mink, although they also have been used for fox and raccoon dogs in emergency situations. The efficacy in eliciting neutralizing antibodies and the safety of three mink-distemper vaccines were studied under field conditions with mink and silver fox. Two of the vaccines were also studied with raccoon dogs and blue fox. All three vaccines elicited a satisfactory antibody response in mink, whereas the response varied in the other species. No side effects were observed in any species tested. One of the vaccines was safe and immunogenic in all four species.

Prevalence of dirofilarial infection in raccoon dogs in Japan

The raccoon dog (Nyctereutes procyonoides viverrinus) is known to acquire canine heartworm (Dirofilaria immitis) infection. We surveyed the prevalence of heartworm infection in free-ranging raccoon dogs in the Nishi-Tama (Tokyo) and Kanagawa areas of Japan. A total of 75 raccoon dog carcasses, including 29 animals from the Nishi-Tama area and 46 from the Kanagawa area, were necropsied between 1992 and 1993. Eight out of 75 raccoon dogs were found to be infected (overall 10.7%). The prevalence of infection was 6 and 16% in Nishi-Tama and Kanagawa, respectively. Microfilarial production was observed in the uterus of one female adult dog.

Emergence, natural history, and variation of canine, mink, and feline parvoviruses

This chapter discusses the emergence of canine parvovirus (CPV), the evidence concerning the previous emergence of mink enteritis virus (MEV) as the cause of a new disease in minks in the 1940s, and the mechanisms that determine the host ranges and other specific properties of the viruses of cats, minks, and dogs. The viruses are classified as the feline parvovirus subgroup of the genus Parvovirus, within the family Parvoviridae. Feline panleukopenia virus (FPV), MEV, and CPV are classified as “host range variants.” In addition to the viruses of cats, minks, and dogs, similar viruses naturally infect many species within the families Felidae, Canidae, Procyonidae, Mustelidae, and possibly the Viverridae. The differences in virulence for minks observed after inoculation of MEV or FPV suggests that there are subtle differences between FPV and MEV that have yet to be defined. Genetic mapping studies indicate that only three or four sequence differences between the FPV and CPV-2 isolates within the VP-1 lVP-2 gene determine all of the specific properties of CPV that have been defined: the pH dependence of hemagglutination, the CPV-specific epitope, and the host range for canine cells and dogs.

Characterization of biological and antigenic properties of raccoon dog and blue fox parvoviruses: a monoclonal antibody study

Parvovirus isolates from blue foxes and raccoon dogs were characterized by studying their haemagglutination properties, host range in vitro and antigenic structure. In all 3 characters, raccoon dog parvovirus resembled canine parvovirus (CPV), while blue fox parvovirus was similar to mink enteritis virus (MEV). Monoclonal antibodies (MAbs) were prepared against both viruses. Raccoon dog parvovirus, while resembling CPV, had a unique antigenic site which could be specified by MAbs. The pattern of MAbs prepared against blue fox parvovirus indicated that it is a member of Type 2 MEV.

Latex agglutination test for detecting feline panleukopenia virus, canine parvovirus, and parvoviruses of fur animals

A latex agglutination (LA) test for the detection of parvoviruses of fur animals, cats, and dogs was developed, and its sensitivity and specificity were compared with those of hemagglutination (HA) and the enzyme-linked immunosorbent assay (ELISA). Tissue culture isolation was used to confirm the specificity results. Fecal samples from various sources were tested, including specimens from raccoon dogs and mink which were experimentally infected with parvoviruses by oral exposure. LA compared favorably with the other tests. The ELISA was the most sensitive. When it was considered as a reference test, the corresponding sensitivities for HA and LA were 96 and 91%, respectively. The specificities were 93% for the ELISA, 95% for the HA test, and 92% for the LA test. LA seems to be a suitable technique for screening animals in the field and in laboratories in which sophisticated techniques are not available.