Eloise L. Styer

Communications: Experimental Production of Proliferative Gill Disease in Channel Catfish Exposed to a Myxozoan-Infected Oligochaete, Dero digitata

Abstract Specific-pathogen-free fry of channel catfish Ictalurus punctatus raised in well water were exposed to Dero digitata (an oligochaete) collected from ponds where catfish have had proliferative gill disease (PGD) and where D. digitata is known to be infected with the triactinomyxid myxozoan Aurantiactinomyxon sp. These fry developed gill lesions and parasites characteristic of PGD. Fry exposed to suspensions of mature Aurantiactinomyxon spores obtained from squashes of infected D. digitata also developed PGD. Fry exposed to oligochaetes other than Dero spp., non-oligochaete benthic macroinvertebrates, or suspensions of squashes of D. digitata without identifiable myxozoans did not develop PGD.

Endometritis in Postparturient Cattle Associated with Bovine Herpesvirus-4 Infection: 15 Cases

Suppurative, ulcerative endometritis associated with bovine herpesvirus-4 (BHV-4) infection was identified in 15 postparturient dairy cows from 5 separate dairies. Characteristic eosinophilic to amphophilic intranuclear viral inclusion bodies were identified within degenerate endometrial lining epithelium and endothelial cells. Bovine herpesvirus-4 was confirmed as the etiology by a combination of fluorescent antibody assays, viral isolation, heminested PCR, ultrastructural examination of the uterus and inoculated tissue culture cells, and negative-stain electron microscopy of tissue culture supernatant. Viral particles measuring 70–95 nm were demonstrated in uterine epithelial and endothelial cells by electron microscopy. Bacteria including Arcanobacterium pyogenes, Escherichia coli, and an α-Streptococcus isolate were isolated from all uteri. Bovine herpesvirus-4-associated endometritis has been previously reported in sporadic cases in Europe but has not been previously reported in the United States. Endometritis associated with BHV-4 appears to be an emerging syndrome in Georgia dairy herds.

Septicemic salmonellosis in two cats fed a raw-meat diet.

Salmonella gastroenteritis and septicemia were diagnosed in two cats presented for necropsy. Both cats resided in the same household and were fed a home-prepared, raw meat-based diet. Salmonella was isolated from multiple organs in both cats and from samples of raw beef incorporated into the diet fed to one of the cats. Subtyping of the bacterial isolates yielded Salmonella newport from one cat and from the diet it had been fed. This report provides evidence that the practice of feeding raw meat-based diets to domestic cats may result in clinical salmonellosis.

Susceptibility of North-American and European crickets to Acheta domesticus densovirus (AdDNV) and associated epizootics

The European house cricket, Acheta domesticus L., is highly susceptible to A. domesticus densovirus (AdDNV). Commercial rearings of crickets in Europe are frequently decimated by this pathogen. Mortality was predominant in the last larval stage and young adults. Infected A. domesticus were smaller, less active, did not jump as high, and the adult females seldom lived more than 10-14 days. The most obvious pathological change was the completely empty digestive caecae. Infected tissues included adipose tissue, midgut, epidermis, and Malpighian tubules. Sudden AdDNV epizootics have decimated commercial mass rearings in widely separated parts of North America since the autumn of 2009. Facilities that are producing disease-free crickets have avoided the importation of crickets and other non-cricket species (or nonliving material). Five isolates from different areas in North America contained identical sequences as did AdDNV present in non-cricket species collected from these facilities. The North American AdDNVs differed slightly from sequences of European AdDNV isolates obtained in 1977, 2004, 2006, 2007 and 2009 and an American isolate from 1988. The substitution rate of the 1977 AdDNV 5kb genome was about two nucleotides per year, about half of the substitutions being synonymous. The American and European AdDNV strains are estimated to have diverged in 2006. The lepidopterans Spodoptera littoralis and Galleria mellonella could not be infected with AdDNV. The Jamaican cricket, Gryllus assimilis, and the European field cricket, Gryllus bimaculatus, were also found to be resistant to AdDNV.

Detection of a Triactinomyxid Myxozoan in an Oligochaete from Ponds with Proliferative Gill Disease in Channel Catfish

Abstract Study of an outbreak of proliferative gill disease in channel catfish Ictalurus punctatus resulted in the detection of triactinomyxid myxozoans in the ponds. Triactinomyxid myxozoan spores were observed in the water above mud samples from ponds that had channel catfish affected with proliferative gill disease. These spores also were found in the gut wall of an oligochaete, Dero digitata, collected from the pond mud. The triactinomyxid myxozoan spores are those of an unidentified species of Aurantiactinomyxon. Dero digitata was present in all ponds with proliferative gill disease on the study farm in 1989. Further studies of a possible relationship between the myxozoan in D. digitata and proliferative gill disease in channel catfish are underway.

Fatal Disease in Nursing Puppies Associated with Minute Virus of Canines

Thirteen cases of a previously undescribed parvoviral infection affecting puppies ranging in age from 5 to 21 days is described. The cases were originally thought to represent an unusual pathologic manifestation of canine parvovirus-2 (CPV-2) infection. However, failure to confirm CPV-2 infection in any of the cases suggested a different parvovirus was involved. Minute virus of canines (MVC) was subsequently isolated from a case by using the Walter Reed Canine Cell Line, the only cell line which will support the growth of MVC. The pathologic and virologic findings for these 13 cases are described in this report.

Occurrence of Piscirickettsiosis-Like Syndrome in Tilapia in the Continental United States

From 2001 to 2003, tilapia (Oreochromis sp.) farms in Florida, California, and South Carolina experienced epizootics of a systemic disease causing mortality. The fish exhibited lethargy, occasional exophthalmia, and skin petechia. The gills were often necrotic, with a patchy white and red appearance. Grossly, the spleen and kidneys were granular with whitish irregular nodules throughout. Granulomatous infiltrates were observed in kidney, spleen, testes, and ovary tissues, but not in the liver. The granulomas contained pleomorphic coccoid bacteria, measuring 0.57 ± 0.1 × 0.8 ± 0.2 μm, that were Giemsa-positive, acid-fast-negative, and Gram-negative. The bacteria had a double cell wall, variable electron-dense and -lucent areas, and were present in the cytoplasm and within phagolysosomes. The syndrome was associated with cold stress and poor water conditions. These findings are consistent with an infectious process caused by a Piscirickettsia-like bacterium described previously in tilapia in Taiwan and Hawaii. This report involves the first identified cases of a piscirickettsiosis-like syndrome affecting tilapia in the continental United States.

Comparative virogenesis of filamentous virus and polydnavirus in the female reproductive tract of Cotesia marginibentris (Hymenoptera: Braconidae)

Abstract A nonoccluded filamentous virus (CmFV) was found in the reproductive tract of females in two of five laboratory colonies of Cotesia marginiventris established from parasitized lepidopteran larvae collected in the southeastern United States. Nucleocapsids of CmFV were 35–39 nm in diameter and had electron-dense cores 21–24 nm in diameter. CmFV virions with a single envelope measured 60–70 nm in diameter; doubly enveloped virions were approximately 90 nm in diameter. The unit length was not determined. CmFV replicated in epithelial cells of the common and lateral oviducts and rarely in small nests of cells in the calyx. CmFV was also transmitted to larvae of the fall armyworm, Spodoptera frugiperda , during parasitization. The ability of C. marginiventris to transmit CmFV increased from Day 1 to Days 3–4 postemergence. A polydnavirus (PV) containing multiple nucleocapsids per envelope occurred in the reproductive tract of females in all five colonies of C. marginiventris . PV replication was limited to the portion of the calyx adjacent to the ovarioles.

Equine Herpesvirus 2-Associated Granulomatous Dermatitis in a Horse

Granulomatous dermatitis in horses has been linked to many etiologies, including various parasites, fungi, and bacteria. Idiopathic forms of granulomatous inflammation-producing diseases, some of which are localized to the skin, also have been reported in horses. Herein we describe a case of recurrent equine granulomatous skin disease characterized by intranuclear viral inclusions within macrophages and giant cells. The histologic changes were primarily noted in the deep dermis and included multifocal to coalescing areas of necrosis marked by histiocytic cell infiltration and presence of giant cells. Electron microscopic examination revealed intranuclear and intracytoplasmic viral particles consistent with herpesvirus. Sequence results of the polymerase chain reaction product were consistent with equine herpesvirus 2, adding another possible etiology to the list of differentials in cases of equine granulomatous skin disease.

Transmission of Ascovirus from Heliothis virescens (Lepidoptera: Noctuidae) by Three Parasitoids and Effects of Virus on Survival of Parasitoid Cardiochiles nigriceps (Hymenoptera: Braconidae)

Abstract In field crops in the southeastern United States, larvae of Heliothis virescens (F.) are often infected with ascoviruses, especially toward the end of the growing season. Ascoviruses are unusual in that they are difficult to transmit per os, and several studies have provided data indicating that these viruses are vectored mechanically by parasitic wasps during oviposition. In Georgia, three parasitoids commonly parasitize H. virescens larvae: Cardiochiles nigriceps Viereck, Campoletis sonorensis (Cameron), and Microplitis croceipes (Cresson). In the current study, we investigated the transmission of ascovirus by these parasitoids by using females that were collected in the field or reared in the laboratory. After a single oviposition by C. nigriceps in an H. virescens larva with a 4-d-old ascovirus infection, all subsequent healthy larvae parasitized by this female developed ascovirus infection. After oviposition in an infected larva, examination of C. nigriceps by using transmission electron microscopy showed that ascovirus virions and ascovirus vesicles adhered to the inner surface of the ovipositor. The ovipositor of M. croceipes was shorter than those of C. nigriceps or C. sonorensis, and this was correlated with a lower rate of ascovirus transmission by the former species. Observation of C. nigriceps populations in the field indicates this species survives even when ascovirus prevalence in H. virescens is high. Laboratory studies of this host–parasite–virus system showed C. nigriceps larvae survived infection of their host if parasitoid larvae were at least second instars at the time of infection. If an ascovirus infection in the first H. virescens host was no older 48 h, a C. nigriceps female sometimes did not transmit ascovirus to subsequent hosts. Exposure to environmental conditions of the field decreased the capacity of C. nigriceps to transmit ascovirus, and transmission also decreased over the longevity of female parasitoids.