Causes of mortality in the Florida panther (Felis concolor coryi).

Panthers necropsied at the University of Florida ranged between 2 weeks and 14 years of age; there were 38 males and 17 females in the cohort. Main categories of causes of death included trauma inflicted from either vehicular collisions (43%) or territorial fights (16%). Specific endogenous diseases involved the respiratory system in 13%, the urinary system in 4%, and the central nervous system in 2%. Ostium secundum atrial septal defects (ASD) were diagnosed in 11% of the panthers necropsied. Seventeen (54%) of the 38 male panthers had either unilateral or bilateral cryptorchidism. Cause of death remained undetermined in 11% of the total cohort.

Altered predation susceptibility of mosquitofish infected with Eustrongylides ignotus.

Eustrongylides ignotus is a parasitic nematode whose definitive hosts are often piscivorous wading birds (Ciconiiformes). Several species of small fishes are intermediate hosts, while larger predatory fish may be paratenic (transport) hosts. We examined predation susceptibility of infected mosquitofish (Gambusia holbrooki) to three species of predatory fishes, including juvenile largemouth bass (Micropterus salminoides), warmouth (Lepomis gulosus), and bluegill (Lepomis macrochirus). A 250 L aquarium with removable plexiglass divider and remote observation windows was constructed. Aquatic macrophytes were placed in the tank to provide refuge for the fishes. Predatory fish were allowed to acclimate to one half of the tank, while one infected and one uninfected mosquitofish were placed in the other. The divider was removed and an observer recorded the number of capture attempts and time required for capture. Predators were observed for behavioral alterations for 4 days after ingestion of infected mosquitofish, then examined at necropsy. Infected prey were selected preferentially in 31 of 38 (82%) trials. The number of capture attempts was 2.7+/-0.2 (x +/- SE) for infected fish and 3.9+/-0.4 for uninfected fish. Mean time of capture was 12.4+/-1.6 min for infected fish and 21.7+/-2.9 for uninfected fish. Because of these differences, infected mosquitofish were more susceptible to predation (P < 0.01) than uninfected fish. Aberrant behavior including lethargy, convulsions, and buoyancy abnormalities was observed in eight (67%) predatory fish. At necropsy, larvae of E. ignotus were found in the coelomic cavity, viscera, and swim bladders of predators. Parasite-induced behavior modification of intermediate hosts may predispose them to predation by wading birds and thereby facilitate the transmission of this nematode in natural populations.

Presence of encysted immature nematodes in a released whooping crane (Grus americana).

Numerous nematode cysts were observed throughout the mesentery and on the surface of gastrointestinal organs in a whooping crane (Grus americana) that was found dead in a central Florida marsh. Morphology of the excysted nematodes most closely resembled third-stage larvae in the order Spirurida but were not similar to any species previously reported in whooping cranes. Evidence presented suggests that the larvae may be Physocephalus sexalatus, a swine spirurid in the subfamily Ascaropsinae that is commonly found encapsulated in birds, amphibians, and reptiles. We suspect that the whooping crane may potentially serve as a transport host for this parasite.

Newcastle disease virus in double-crested cormorants in Alabama, Florida, and Mississippi.

In order to understand the epidemiology of Newcastle disease (ND) outbreaks in double-crested cormorants (Phalacrocorax auritus), a study was conducted on wintering migratory cormorants (P. a. auritus) in Alabama and Mississippi (USA) and non-migratory cormorants (P. a. floridanus) that breed in Florida (USA). Antibodies against ND virus were detected by the hemagglutination-inhibition method in sera from 86 of 183 (47%) migratory cormorants over-wintering in eight roosting sites in Alabama and Mississippi between November, 1997 and April, 1999. Titers ranged from 5 to 40. Antibody prevalences in sera collected from females in early winter (November and December) (26%) and late winter (February and March) (56%) were significantly different (P = 0.0007). None of 45 serum samples from 1- to 7-wk-old nestlings from 11 colonies in Florida during the 1997-98 and 1998-99 breeding seasons was positive. However, antibodies were detected in yolk samples from 98 of 126 (78%) eggs collected in these same colonies. Titers ranged from 4 to 256. The prevalence of antibodies in eggs collected from fresh-water colonies (63% prevalence, n = 30) and salt-water colonies (82% prevalence, n = 96) was significantly different (P = 0.041). ND virus was not isolated from tissues of 18 cormorants and cloacal and tracheal swabs from 202 cormorants collected in Alabama and Mississippi; virus was also not isolated from cloacal and tracheal swabs from 51 nestlings from Florida.

Methylmercury accumulation in tissues and its effects on growth and appetite in captive great egrets.

To test the hypothesis that fledging wading birds would be more at risk from mercury toxicosis than younger nestlings, captive great egret nestlings were maintained as controls or were dosed from 1- to 14-wk-old with 0.5 or 5 mg methylmercury chloride/kg wet weight in fish. Birds dosed with 5 mg/kg suffered from subacute toxicosis at wk 10-12. Growing feather concentrations were the most closely correlated with cumulative mercury consumed per weight. Blood concentrations of mercury increased more rapidly after 9 wk in all groups when feathers stopped growing. Total mercury accumulated in tissues in concentrations in the following order: growing scapular feathers > powderdown > mature scapular feathers > liver > kidney > blood > muscle > pancreas > brain > bile > fat > eye. The proportion of total mercury that was methylated depended upon tissue type and dose group. Selenium accumulated in liver in direct proportion to liver mercury concentrations. After wk 9, appetite and weight index (weight/bill length) declined significantly in both dosed groups. At current exposure levels in the Everglades (Florida, USA) mercury deposited in rapidly growing feathers may protect nestlings from adverse effects on growth until feathers cease growing.

Histologic, neurologic, and immunologic effects of methylmercury in captive great egrets.

Captive great egret (Ardea albus) nestlings were maintained as controls or were dosed with methylmercury chloride at low (0.5), and high doses (5 mg/kg, wet weight) in fish. Low dosed birds were given methylmercury at concentrations comparable to current exposure of wild birds in the Everglades (Florida, USA). When compared with controls, low dosed birds had lower packed cell volumes, dingy feathers, increased lymphocytic cuffing in a skin test, increased bone marrow cellularity, decreased bursal wall thickness, decreased thymic lobule size, fewer lymphoid aggregates in lung, increased perivascular edema in lung, and decreased phagocytized carbon in lung. High dosed birds became severely ataxic and had severe hematologic, neurologic, and histologic changes. The most severe lesions were in immune and nervous system tissues. By comparing responses in captive and wild birds, we found that sublethal effects of mercury were detected at lower levels in captive than in wild birds, probably due to the reduced sources of variation characteristic of the highly controlled laboratory study. Conversely, thresholds for more severe changes (death, disease) occurred at lower concentrations in wild birds than in captive birds, probably because wild birds were exposed to multiple stressors. Thus caution should be used in applying lowest observed effect levels between captive and wild studies.

Effects of mercury on health and first-year survival of free-ranging great egrets (Ardea albus) from southern Florida.

The objectives of this study were to determine whether elevated mercury (Hg) concentrations have a negative impact on the health and survival of nestling and juvenile free-ranging great egrets (Ardea albus) from southern Florida. During 1994, when health and survival was monitored in a cohort of young birds with naturally variable concentrations of Hg, packed cell volume was positively correlated with blood Hg concentrations, and high Hg concentration in blood was not related to the probability of surviving during the first 10.5 months of life. During 1995, 70 first-hatched great egret chicks were included in a Hg field-dosing experiment to compare the effects of elevated Hg on health and survival. Birds were dosed while in the nest orally every 2.5 days for 15 days with 0.5 mg of methyl mercury chloride (MeHgCl) for an estimated intake of 1.54 mg MeHgCl/kg food intake. These birds were compared with controls, which received an estimated 0.41 mg MeHgCl/kg food. No differences were observed in health parameters or in the probability of surviving during the first 8 months of age between egrets that were dosed with Hg and those that were not. A likely explanation for the lack of any effects on health and survival between both groups could be that chicks at this age were eliminating most of the dietary Hg through the production of new feathers.

New records of subcutaneous mites (Acari:Hypoderatidae) in birds, with examples of potential host colonization events.

New host, geographic records, or both are established for 14 species of hypoderatid deutonymphs from 14 species of birds in North America. Ten of these records are regarded as examples of a potential host colonization event where these hypopi have become established in hosts other than those with which they are normally associated. Herein, potential host colonization events by hypoderatid deutonymphs are regarded as more of an ecologically determined than physiologically specific phenomenon, often specifically related to sharing of nesting sites in the same rookeries by different host taxa. Neottialges ibisicola Young & Pence is placed as a junior synonym of Neottialges plegadicola Fain. The taxonomic status of Hypodectes propus from columbid versus ardeid hosts needs further study.

Prevalence of Eustrongylides ignotus in mosquitofish (Gambusia holbrooki) in Florida: historical and regional comparisons.

We examined mosquitofish (Gambusia holbrooki) caught between January 1990 and December 1991 from 24 sites in northern Florida (USA), and preserved specimens collected from 32 sites throughout Florida between 1930 and 1978, for presence of the larval nematode Eustrongylides ignotus. We found 10 (42%) of the 24 recently-sampled sites in northern and central Florida had at least one larval nematode present in the fish; combining these data with results of previous work, 11 (15%) of 75 recently sampled sites throughout Florida had at least one nematode. By comparison, in the museum collections fish from only one (3%) of the 32 sites had the nematode, and none in northern Florida.

Hypopi (Acari: Hypoderatidae) from the roseate spoonbill (Aves: Ciconiiformes; Threskiornithidae).

A new species and additional host records for 4 other species of quiescent deutonymphs (hypopi) of mites of the family Hypoderatidae are described from the subcutaneous adipose tissues of a roseate spoonbill, Ajaia ajaja L., in Florida. The hypopus of Phalacrodectes parvus n. sp. most closely resembles that of P. platalea Pence & Duncan from the African spoonbill, Platalea alba Scopali, in idiosomatic chaetotaxy and structure of the genital apparatus. It differs from this and other species of the genus in the shape of the idiosoma, pattern and density of idiosomatic sclerotization, the unique posterior extension of secondary sclerotization from the perigenital area, large size and more posterior location of genital seta gm, and small size and sharp-tipped spinelike structure of seta hT on tibia II. In addition to the new species, this roseate spoonbill also was infected with P. whartoni Fain and 3 other less common species of hypoderatid deutonymphs. A key to the deutonymphs of species in the genus Phalacrodectes is presented.

Helminth and arthropod parasites of experimentally introduced whooping cranes in Florida.

Nine species of nematodes, unidentified larval nematodes, three species of trematodes, two species of acanthocephalans and a single species of chewing louse were collected from 1993 to 1995 from 25 introduced whooping cranes (Grus americana) in Florida (USA). In spite of a quarantine procedure involving anthelmintic therapy, three helminth parasites may have been introduced from captive populations. Other parasites acquired were similar to those found in a local congener, the Florida sandhill crane (Grus canadensis pratensis), or only occurred infrequently.

A species of Plasmodium from sandhill cranes in Florida.

Infections of a species of Plasmodium (subgenus Giovannolaia) were diagnosed in 3 sandhill cranes (Grus canadensis) from north-central Florida. This parasite is close morphometrically to Plasmodium polare; this finding constitutes the first report of a species of Plasmodium from sandhill cranes in North America.

Arboviruses in water birds (Ciconiiformes, Pelecaniformes) from Florida.

Sera from 360 ciconiform and pelecaniform birds collected in Florida (USA) from 1974 to 1990 were tested for serum neutralizing (SN) antibodies to eastern equine encephalitis (EEE), St. Louis encephalitis (SLE), and Everglades (EVE) viruses. Serum neutralizing antibodies to EEE virus were detected in 2%, to SLE virus in 7%, and to EVE virus in none of the samples. Pelecaniform birds (16%) had a higher antibody prevalence (P < 0.02) for SLE virus than did ciconiform birds (5%). Virus could not be isolated from 67 samples. Nestling birds with SN antibodies to both EEE and SLE viruses were found in both fresh water and marine colonies. Antibodies were more prevalent in adult and fledged juvenile birds than in nestlings.

Sarcocystis sp. in wading birds (Ciconiiformes) from Florida.

Sarcocysts were found in striated muscle of 21 adult wading birds among 145 examined grossly and 70 examined histologically (calculated prevalence = 24%), and in none of 332 immature wading birds examined from Florida (USA). Six of 12 species of ciconiforms were infected (Ardea herodias, Casmerodius albus, Egretta caerulea, Nyctanassa violacea, Butorides striatus, Eudocimus albus). Cysts were filamentous, usually extended the entire length of the muscle fiber, and were visible grossly in 33% of the positive cases. We concluded from ultrastructural examination of cysts that the same species of Sarcocystis may occur in all species of wading birds in Florida; however, two cyst diameters were noted that appeared to differ in their distribution by host species.

The epizootiology of eustrongylidosis in wading birds (Ciconiiformes) in Florida.

A total of 2,167 individuals representing 15 species of wading birds was examined for infection with the nematode Eustrongylides ignotus in Florida (USA). Ten of the species were infected with the greatest prevalences occurring in great blue herons (Ardea herodius) (33%), great egrets (Casmerodius albus) (22%), and snowy egrets (Egretta thula) (19%). Among nestlings, prevalences increased with age. This parasite was estimated to cause at least 80% mortality among nestling ciconiiforms at one colony in Everglades National Park, and was found in 15% of nestling ardeids throughout the state. Despite wide sampling efforts, infected fish (second intermediate hosts) were only found at six sites in Florida, all of which had been physically altered, such as with canals and ditches, and had an anthropogenic (human-caused) source of nutrient pollution. Colonies near sources of infected fish experienced significantly higher prevalences of eustrongylidosis that did colonies for which no source of infected fish could be found within 20 km. Higher prevalences were found at freshwater and estuarine mainland colonies than at marine colonies. Densities of aquatic oligochaetes, which may act as first intermediate hosts, were highest at sites containing infected fish and at sites with a source of nutrient pollution. Conservation and management of wading bird species should include consideration of this disease, epizootics of which seem to be linked to nutrient pollution.

Pathogenesis of Eustrongylides ignotus (Nematoda: Dioctophymatoidea) in Ciconiiformes.

Natural (n = 157) and experimental (n = 5) infections with the nematode Eustrongylides ignotus are described for ciconiforms collected in Florida (USA). Larvae perforated the ventriculus in 3 to 5 hr and caused hemorrhage and bacterial peritonitis that sometimes progressed to a fibrous peritonitis with extensive adhesions. Severity of the disease was related inversely to the age of the bird and directly to the number of parasites involved. Some infections in adult birds were resolved. As a consequence of eustrongylidosis, anorexia and behavioral abnormalities resulted in emaciation and may have predisposed birds to traumatic death. Host-parasite adaptations apparently were not adequate for nestling ciconiforms as death of nestlings usually occurred before infections become patent (longer than 14 days, less than 23 days). Patent infections were found in both color morphs of the great blue heron (Ardea herodius), and in great egrets (Casmerodius albus) and snowy egrets (Egretta thula). We propose that birds of the family Ardeidae are the primary definitive hosts.

Demodicosis in black bears (Ursus americanus) from Florida.

Demodicosis was diagnosed in five black bears (Ursus americanus) from north-central Florida. The first bear examined, a 5-yr-old male, had severe alopecia except for the dorsal neck, paws, and ears. The skin was characterized by moderate orthokeratotic hyperkeratosis, and mild to moderate follicular hyperkeratosis. Superficial dermatitis, follicular pustules, and epidermal pustules were present, but rare. Specimens of Demodex sp. were seen most commonly within hair follicles devoid of hair and at the infundibulum of sebaceous glands. Four additional bears from the same area also had some degree of alopecia and skin scrapings were positive for Demodex sp. This mite may be common, although its prevalence is not known.

Chondrosarcoma in a wild great white heron from southern Florida.

A typical chondrosarcoma is reported from the nictitating membrane of a great white heron (Ardea herodius occidentalis). This is the first report of a neoplasm in a free flying ciconiiform, and was the only one found in a survey of 957 carcasses from Florida.