Geographic information systems and the environmental risk of schistosomiasis in Bahia, Brazil.

A geographic information system was constructed using maps of regional environmental features, Schistosoma mansoni prevalence in 30 representative municipalities, and snail distribution in Bahia, Brazil to study the spatial and temporal dynamics of infection and to identify environmental factors that influence the distribution of schistosomiasis. Results indicate that population density and the duration of annual dry period are the most important determinants of prevalence of schistosomiasis in the areas selected for study. Maximum rainfall, total precipitation during three consecutive months, annual maximum or minimum temperatures, and diurnal temperature difference were not shown to be significant factors influencing S. mansoni prevalence in local populations or distribution of snail hosts. Prevalence of the disease was highest in the coastal areas of the state. Higher prevalence tended to occur in areas with latossolo soil type and transitional vegetation.

A model of Staphylococcus aureus bacteremia, septic arthritis, and osteomyelitis in chickens.

We studied the occurrence, magnitude, and kinetics of bacteremia and the resultant osteomyelitis and septic arthritis in an avian model of Staphylococcus aureus infection. Thirty-day-old male broiler chicks were inoculated i.v. with 10(5), 10(6), or 10(7) cfu of strain Duntravis, a beta-hemolytic, coagulase-producing, capsular type 8 isolate from the synovial fluid of a 2-year-old black boy. Bacteremia occurred in 80%, 90%, and 100% of animals inoculated with 10(5), 10(6), or 10(7) cfu, respectively. The magnitude of bacteremia in surviving, bacteremic animals increased for 96 hours after inoculation and then decreased after a plateau phase. Osteomyelitis and septic arthritis occurred only in chicks that were continuously bacteremic. The occurrence of osteomyelitis was uniform among continuously bacteremic animals and developed 1 to 23 hours after inoculation. Chickens are susceptible to systemic infections with S. aureus. Bacteremia, osteomyelitis, and septic arthritis may be induced in healthy chickens without prior manipulations that depress their resistance.

Preliminary findings of Salmonella spp. in captive green iguanas (Iguana iguana) and their environment.

Captive reptiles are routinely identified as reservoirs of Salmonella spp. and reports of reptile-associated salmonellosis are increasing. Unfortunately, little is known about the epidemiology of Salmonella spp. and green iguanas. We did a limited survey of a green-iguana farm in El Salvador to identify sources of Salmonella spp. in green iguanas and their environment. A limited number of samples for microbiological culture were collected from iguanas (adult, hatchling, and embryos) and their environment (food, water, soil, shelter, insects, and wild-caught lizards). Salmonella spp. was isolated from the intestine of both adult (3/20) and hatchling iguanas (8/20). There was no evidence of Salmonella spp. in the reproductive tracts of female iguanas (0/10). Salmonella spp. was isolated from the surface of 40% (7/16) of the egg surfaces tested. Salmonella spp. was not identified from the externalized yolk-sac of the iguana embryos tested. Soil samples from a breeding pen and a nest were both positive for Salmonella spp. Eight different Salmonella spp. serotypes were identified in this survey. These results suggest that horizontal transmission of Salmonella spp. is a potential source of exposure to hatchling iguanas at this facility.

Evaluation of alternative strategies to prevent Newcastle disease in Cambodia.

Velogenic viscerotropic Newcastle disease (vvNCD), which is endemic in Cambodia, can be prevented in theory by a combination of biosecurity and immunization of broiler flocks. The relative contribution of appropriate biosecurity and effective vaccination was quantified at the farm level, applying realistic projections for capital investment, fixed and variable production costs and losses following infection. Non-protected broiler flocks generate a loss when the probability of vvNCD infection exceeds 0.4. Applying both biosecurity and effective vaccination would sustain profitability up to a probability of exposure of 1.0. The benefit to cost ratios for alternative strategies were evaluated for a range of probabilities of exposure to vvNCD extending from 0.1 to 1.0. The benefit-to-cost ratio for biosecurity exceeded unity at a risk of exposure exceeding 0.1, and 0.2 for vaccination and the combination of vaccination and biosecurity respectively. A sensitivity analysis demonstrated that the efficiency of protection, feed cost, and financial consequences of infection markedly affected the projected benefit-to-cost ratios associated with alternative methods of prevention.

Prevalence and pathogenicity of Aeromonas hydrophila.

A field survey to determine the prevalence of Aeromonas hydrophila revealed a recovery rate of 8% in 141 specimens derived from a range of live, companion, and exotic avian species. The prevalence rate was similar in 240 sequential postmortem submissions during 1984. Studies on the pathogenicity of A. hydrophila showed that 2-to-4-day-old chicks and turkey poults were highly susceptible to exposure via the subcutaneous, yolk-sac, and intracerebral routes, and mortality of 80-100% occurred within 48 hours of inoculation. Ducklings aged 4 days were generally refractory to exposure.

Prevalence of Campylobacter jejuni in selected domestic and wild birds in Louisiana.

Prevalence of Campylobacter jejuni was determined in a selected population of domestic and free-living birds submitted for necropsy to the Louisiana State Veterinary Medical Diagnostic Laboratory. The 445 cases examined included 13 orders of birds and yielded C. jejuni in 45 cases, representing an isolation rate of 10.1%. Prevalence was highest in Galliformes (25.2%), followed by Anseriformes (12.9%) and Columbiformes (8.3%). Only one isolation was made out of 179 Psittaciformes examined. Penner serotypes 1, 2, 4, and 16 were most commonly identified among the C. jejuni isolates. This study emphasizes the importance of Galliformes as reservoirs of C. jejuni. The commonality of these serotypes with isolates derived from humans suggests the zoonotic potential of Galliformes in relation to human campylobacteriosis. The isolation rate of 12.9% in Anseriformes implicates free-living and migratory waterfowl as carriers of C. jejuni. Results confirm that Psittaciformes represent a low risk of C. jejuni infection in humans.

Role of litter in the transmission of Campylobacter jejuni.

Autoclaved or non-autoclaved used broiler litter that was experimentally contaminated with Campylobacter jejuni was capable of infecting specific-pathogen-free chicks maintained in modified Horsfall isolators. Artificially infected chicks became fecal shedders of C. jejuni, resulting in contamination of both autoclaved and non-autoclaved used broiler litter. Fecal shedding of C. jejuni by litter-reared, artificially infected chicks persisted for at least 63 days after chicks were transferred to an isolation unit with a wire floor, which prevented coprophagy. C. jejuni was consistently recovered from water and litter in units housing directly and indirectly infected birds, indicating environmental contamination. These experiments demonstrate the potential role of litter in the perpetuation and transmission of C. jejuni infection in commercial chickens.

Transmission of Campylobacter jejuni by the housefly (Musca domestica).

Houseflies (Musca domestica) were infected with Campylobacter jejuni after being confined for 5 days in a Horsfall isolator containing 25-day-old chickens known to be fecal excretors of the organism. Contaminated flies, when subsequently transferred to a second unit, transmitted C. jejuni to specific-pathogen-free chickens. Allowing a sample of 32 houseflies to ingest C. jejuni in a liquid suspension resulted in recovery rates of 20% from the feet and ventral surface of the body and 70% from the viscera. These experiments demonstrated the potential role of flies in the dissemination of avian campylobacteriosis.

Encephalitis attributed to dactylariosis in Japanese quail chicks (Coturnix coturnix japonica).

Dactylaria gallopava was isolated from brain tissue of 1-to-3-week-old quail chicks. Successive batches demonstrated elevated (15-20%) mortality preceded by incoordination and lateral recumbency. Chicks exhibited cerebellar and cerebral encephalitis characterized by brown-red discoloration of affected brain tissue. Decontamination of setters and hatchers resulted in abrupt cessation of mortality in subsequent placements, implicating incubators as the source of infection.

The occurrence of Clostridium perfringens in the intestine of chicks.

Commercial broiler chicks brooded either on wire or on used or new litter demonstrated a 75% (62/75) incidence of recovery of "perfringens-like" colonies from the intestine during a 5-week period. Eleven Clostridium spp. were identified from among these "perfringens-like" organisms, which were cultured on SPS selective agar medium. Clostridium perfringens was positively identified only infrequently (five isolates) from among the "perfringens-like" colonies. In contrast, "perfringens-like" colonies were not recovered from the intestinal contents of specific-pathogen-free chicks reared in an isolation unit. However, C. perfringens was isolated from the yolk sac of one embryonated egg and from the intestine of a single 7-day-old chick, indicating the possibility of vertical transmission of this potential pathogen.

The occurrence of Aeromonas hydrophila in avian diagnostic submissions.

Twenty isolations of Aeromonas hydrophila were made from 15 species of free-living, commercial, and companion birds submitted for routine diagnostic postmortem examination. Seventy percent of the isolations were made from November through March during the 25-month survey period.

Enhancement of Campylobacter jejuni virulence by serial passage in chicks.

Four isolates of Campylobacter jejuni were studied to determine changes in virulence following six serial passages in chicks. Chicks that received invasive isolates exhibited diarrhea and depressed weight gain. Immature mice were used to assess virulence of the passaged isolates of C. jejuni. Nine-day-old mice infected with passaged isolates showed lethargy, dehydration, depression, decreased weight gain, and occult blood in feces. Mouse pups inoculated with the third and sixth chick passage levels of an invasive isolate showed significant depression in mean daily weight gain and elevated mortality compared with controls and subjects inoculated with unpassaged isolates. This study demonstrated enhancement of virulence in a C. jejuni isolate following chick passage. In contrast, three other passaged isolates failed to show any consistent increase in virulence.

Tuberculosis in commercial emus (Dromaius novaehollandiae).

Extensive granuloma formation typical of tuberculosis was observed in a mature female emu. The diagnosis was confirmed by demonstration of acid-fast bacilli in lesions and culture of a Mycobacterium with growth characteristics resembling M. avium from liver tissue. Individual emus on the affected farm and an epidemiologically related unit gave a positive skin reaction to intradermal M. avium tuberculin. The implication of tuberculosis in commercial emus is noted in relation to the growth of the industry in North America and to management and commercial practices that encourage dissemination of infection within the species and to other exotic and domestic animals.

Comparison of procedures to detect Chlamydia psittaci antibodies in cockatiels (Nymphicus hollandicus).

Diagnostic serologic procedures for psittacine chlamydiosis were evaluated using experimentally inoculated cockatiels (Nymphicus hollandicus). Chlamydia psittaci was recovered from subjects on day 16 postinoculation. Seroconversion was confirmed by the direct complement fixation (DCF) test. The blocking enzyme-linked immunosorbent assay was demonstrated to be the most sensitive of three serodiagnostic procedures evaluated from inoculation until day 24 postinfection, with 92% sensitivity and 73% specificity. The DCF test was progressively more sensitive over the duration of the experiment, attaining 100% sensitivity and specificity on the day 24 postinfection. This study confirms the ability of the DCF procedure to adequately detect C. psittaci antibodies. Limitations relating to reproducibility of serologic results under clinical conditions found in this study indicate that a further refinement of tests is required to consistently detect and quantify antibodies.

Effects of pH, temperature, and salinity on persistence of avian influenza viruses in water.

The combined effects of water temperature, salinity, and pH on persistence of avian influenza virus (AIV) were evaluated in a model distilled-water system using three isolates from ducks sampled in Cameron Parish, Louisiana. Variables were tested within the ranges normally associated with surface water. Differences were detected between temperature (17 C and 28 C), pH (6.2, 7.2, 8.2), and salinity (0 ppt and 20 ppt), with a strong interactive effect observed between pH and salinity. Estimated persistence of infectivity for 1 x 10(6) mean tissue-culture infective dose of A/mottled duck/LA/38M/87 (H6N2) was longest at 17 C/0 ppt/pH 8.2 (100 days) and shortest at 28 C/20 ppt/pH 8.2 (9 days). Differences in the response to these variables were apparent between viruses. The ability of AIV to persist in surface water was also evaluated using samples collected from varied waterfowl habitats in coastal Louisiana. Observations were consistent with the model system, with duration of infectivity decreasing with increased salinity and pH. This suggests that experimental results may have application to field conditions.

Persistence of avian influenza viruses in water.

Persistence of five avian influenza viruses (AIVs) derived from four waterfowl species in Louisiana and representing five hemagglutinin and neuraminidase subtypes was determined in distilled water at 17 C and 28 C. Infectivity was determined over 60 days by microtiter endpoint titration. One AIV was tested over 91 days at 4 C. Linear regression models for these viruses predicted that an initial concentration of 1 x 10(6) TCID50/ml water could remain infective for up to 207 days at 17 C and up to 102 days at 28 C. Significant differences in slopes for AIV persistence models were detected between treatment temperatures and among viruses. Results suggest that these viruses are adapted to transmission on waterfowl wintering habitats. Results also suggest a potential risk associated with waterfowl and domestic poultry sharing a common water source.

Avian influenza viruses from migratory and resident ducks of coastal Louisiana.

Cloacal and tracheal swabs were collected from 1389 hunter-killed ducks in Cameron Parish, Louisiana, during the 1986 and 1987 waterfowl seasons. Twenty-eight avian influenza viruses (AIVs) were isolated from 605 blue-winged teal (Anas discors), 75 mottled ducks (A. fulvigula), 375 gadwalls (A. stepera) and 334 green-winged teal (A. crecca). Prevalence estimates of AIV in ducks sampled during September, November, and December through January were 3.1%, 2.0%, and 0.4%, respectively. Differences in prevalence were detected by season (P = 0.044) and age class (P = 0.036). Two isolations from resident mottled ducks document transmission of AIV on these wintering areas. Much subtype diversity was present, with nine of 13 hemagglutinin (HA) and nine of nine neuraminidase (NA) subtypes recovered. Predominant HA and NA subtypes were typical of AIVs commonly associated with waterfowl. Results indicate that AIVs are transmitted in the wintering areas, and, although prevalence is low, these viruses continue to circulate within these duck populations during winter.

Evaluation of biosecurity in broiler breeders.

The economic impact of management practices designed to limit the introduction of disease into a parent broiler breeder flock (biosecurity) was evaluated using benefit-cost analysis. Equations were developed to quantify the losses resulting from infection with one of four alternative categories of disease representing incremental levels of pathogenicity. Realistic costs and assumed values relating to the probability of infection were used to evaluate the ameliorative effect of three alternative levels of biosecurity. A microcomputer spreadsheet program was used to confirm that expenditure on protective measures can be justified by both the risk of introducing a disease and the magnitude of losses that may occur following infection.

Eastern equine encephalitis in a flock of emus (Dromaius novaehollandiae).

Eastern equine encephalitis (EEE) was diagnosed in a flock of emus in southeastern Louisiana. The outbreak involved juvenile and adult breeders ranging in age from 20 to 36 months, with an attack rate of 76% and a case fatality rate of 87%. The diagnosis was confirmed by isolation and characterization of the viral agent, and by detection of EEE antibody in two recovered emus. High mortality was preceded by marked depression, hemorrhagic diarrhea, and emesis of blood-stained ingesta. On postmortem examination, hemorrhagic enteritis and multiple petechia of viscera were observed. Microscopic changes included severe necrosis of hepatocytes, intestinal mucosa, and necrotizing vasculitis of the spleen and lamina propria of the intestine. No nervous system lesions were observed. This outbreak occurred concurrently with EEE in horses and was attributed to unseasonably heavy rainfall with an abundance of arthropod vectors and proximity to free-living reservoir host species.

Campylobacter infection of commercial poultry.

Campylobacter jejuni, a widespread food-borne pathogen is responsible for enteritis in the populations of both industrialised and developing nations and is acquired by consumption of contaminated water, milk and food products. Contaminated poultry meat is regarded as an important source of campylobacteriosis, with both commercial broiler and turkey growing flocks infected at two to three weeks of age by direct and indirect horizontal exposure. Non-chlorinated water is regarded as a vehicle of infection, followed by rapid intraflock dissemination. Intensification in the poultry industry has contributed to the increased prevalence rates on carcasses associated with increased stocking density and mechanized processing which are inherent to the high efficiency dictated by a competitive market. Currently, pre- and post-harvest control measures may ameliorate the problem of Campylobacter infection in consumers. Refrigerated storage and transport of red meat and poultry, appropriate handling and food preparation, and thorough cooking reduce the possibility of food-borne infection. In view of the world-wide distribution of C. jejuni infection and the multiplicity of sources, including non-pasteurised milk and contaminated water, it is inappropriate to impose trade restrictions on poultry meat based on the detection of campylobacters.