Prevalence and disease caused by isosporoid coccidia in passerine birds are well recognized, but confusion about the life cycles of the parasites has led to taxonomic inconsistencies. In this study, we characterized segments of the chromosomal small and large-subunit ribosomal RNA (rRNA) genes of coccidial parasites from 23 species of passerine birds, as well as heat shock protein 70, apicoplast rRNA, and chromosomal 5.8s rRNA genes from a subgroup of these animals, and we correlated genetic data with morphologic findings for different parasite developmental stages, host phylogeny, and overall taxonomic relations within the phylum Apicomplexa. Our findings indicate that isosporoid coccidia of passerine birds are monophyletic but exhibit substantial diversity, with most avian species having one or several unique parasite lineages that underwent synchronous speciation with their hosts, interrupted by sporadic episodes of lateral transmission across species and families. Molecular analyses support a homoxenous life cycle, with sexual forms occurring chiefly in the intestines and asexual merozoites present systemically. Rarely, extraintestinal sexual stages can occur. The passerine coccidia are genetically most closely related to species of Eimeria rather than Isospora. We suggest that these parasites, whether identified from blood merozoite stages or fecal oocysts, be provisionally grouped as a homogeneous clade of individual species in a single taxon and formally named when reliable criteria allowing reclassification of related genera in the suborder Eimeriina are clarified.

In 1996, a disease outbreak occurred at a captive breeding facility in Idaho, causing anorexia, dehydration, and diarrhea or sudden death in 72 of 110 Northern aplomado falcons (Falco femoralis septentrionalis) from 9 to 35 days of age and in 6 of 102 peregrine falcons (Falco peregrinus) from 14 to 25 days of age. Sixty-two Northern aplomado and six peregrine falcons died. Epidemiologic analyses indicated a point source epizootic, horizontal transmission, and increased relative risk associated with cross-species brooding of eggs. Primary lesions in affected birds were inclusion body hepatitis, splenomegaly, and enteritis. The etiology in all mortalities was determined by molecular analyses to be a new species of adenovirus distantly related to the group I avian viruses, serotypes 1 and 4, Aviadenovirus. In situ hybridization and PCR demonstrated that the virus was epitheliotropic and lymphotropic and that infection was systemic in the majority of animals. Adenoassociated virus was also detected by PCR in most affected falcons, but no other infectious agents or predisposing factors were found in any birds. Subsequent to the 1996 epizootic, a similar disease caused by the same adenovirus was found over a 5-year period in orange-breasted falcons (Falco deiroleucus), teita falcons (Falco fasciinucha), a merlin (Falco columbarius), a Vanuatu peregrine falcon (Falco peregrinus nesiotes), and gyrfalcon ؋ peregrine falcon hybrids (Falco rusticolus/peregrinus) that died in Wyoming, Oklahoma, Minnesota, and California. These findings indicate that this newly recognized adenovirus is widespread in western and midwestern North America and can be a primary pathogen in different falcon species.

A family of three white-faced saki monkeys (Pithecia pithecia pithecia) died 48-96 hours after the onset of anorexia, nasal discharge, pyrexia and oral ulceration. One animal also had clonic seizures. Lesions found post-mortem consisted of oral and esophageal ulcers, hepatic and intestinal necrosis, meningoencephalitis and sporadic neuronal necrosis. Intranuclear inclusion bodies and syncytial cells were present in oral lesions and affected areas of liver. Herpes simplex virus 1 (HSV-1) was identified as the etiology of disease by virus isolation, polymerase chain reaction, or in situ hybridization in all three animals. Immunohistochemistry for detection of apoptotic DNA and activated caspase-3 showed significant levels of apoptosis in oral and liver lesions and occasional apoptotic neurons in the brain. These findings demonstrate the vulnerability of white-faced saki monkeys to HSV-1 and provide initial insight into the pathogenesis of fatal HSV-1-induced disease, indicating that apoptosis plays a significant role in cell death.

Eight Barbary red deer (Cervus elaphus barbarus) developed clinical signs suggestive of malignant catarrhal fever (MCF) over a 28-day period. These animals were housed outdoors with four other species of ruminants. Affected red deer had lethargy, ocular signs, and nasal discharge and were euthanatized within 48 h. Lesions included ulcers of the muzzle, lips, and oral cavity associated with infiltrates of neutrophils and lymphocytes. Serologically, six of seven red deer tested during the outbreak were positive by competitive enzyme-linked immunosorbent assay for antibodies to a shared MCF virus antigen. PCR using oligonucleotide primers designed for a conserved protein of alcelaphine herpesviruses 1 (AlHV-1) and 2 (AlHV-2) and for conserved regions of a herpesvirus DNA polymerase gene was positive for tissues from all eight clinically affected animals and negative for eight out of eight red deer without clinical signs of MCF. DNA sequencing of PCR amplicons from the diseased red deer indicated that they were infected with a novel herpesvirus closely related to AlHV-2; immunohistochemistry using polyclonal anti-AlHV-2 serum and in situ hybridization demonstrated the presence of virus within salivary glands adjacent to oral lesions of affected animals. A survey of other ruminants near the outbreak subsequently showed that normal Jackson's hartebeest (Alcelaphus buselaphus jacksoni) that were cohoused with the diseased red deer were infected with the same virus and were shedding the virus in nasal excretions. These findings suggest that a herpesvirus closely related to AlHV-2 caused the MCF-like disease epizootic in Barbary red deer and that the virus may have originated from Jackson's hartebeest.

Seven of 28 passerine birds that died in captivity were positive for malarial parasites by polymerase chain reaction targeting the mitochondrial cytochrome b (cytB) and apicoplast ribosomal RNA (rRNA) genes. Each bird was infected with a single parasite lineage having a unique genotype. Apicoplast rRNA sequences were present both in Haemoproteus spp. and Plasmodium spp. and had typically high adenosine + thymidine content. Phylogenies for cytB and apicoplast rRNA sequences were largely congruent and supported previous studies that suggest that Plasmodium-Haemoproteus spp. underwent synchronous speciation with their avian hosts, interrupted by sporadic episodes of host switching. Apicoplast phylogeny further indicated that Haemoproteus spp. are ancestral to Plasmodium spp. All the 7 infected passerine birds had histologic lesions of malaria, and malarial parasites may have contributed to the death of at least 4 animals. These findings provide new genetic data on passerine hematozoa, including initial sequences of apicoplast DNA, and emphasize the relevance of parasite prevalence, evolutionary relationships, and host switching to modern management and husbandry practices of captive birds.