BackgroundInstitutional tuberculosis (TB) transmission is an important public health problem highlighted by the HIV/AIDS pandemic and the emergence of multidrug- and extensively drug-resistant TB. Effective TB infection control measures are urgently needed. We evaluated the efficacy of upper-room ultraviolet (UV) lights and negative air ionization for preventing airborne TB transmission using a guinea pig air-sampling model to measure the TB infectiousness of ward air.Methods and FindingsFor 535 consecutive days, exhaust air from an HIV-TB ward in Lima, Perú, was passed through three guinea pig air-sampling enclosures each housing approximately 150 guinea pigs, using a 2-d cycle. On UV-off days, ward air passed in parallel through a control animal enclosure and a similar enclosure containing negative ionizers. On UV-on days, UV lights and mixing fans were turned on in the ward, and a third animal enclosure alone received ward air. TB infection in guinea pigs was defined by monthly tuberculin skin tests. All guinea pigs underwent autopsy to test for TB disease, defined by characteristic autopsy changes or by the culture of Mycobacterium tuberculosis from organs. 35% (106/304) of guinea pigs in the control group developed TB infection, and this was reduced to 14% (43/303) by ionizers, and to 9.5% (29/307) by UV lights (both p < 0.0001 compared with the control group). TB disease was confirmed in 8.6% (26/304) of control group animals, and this was reduced to 4.3% (13/303) by ionizers, and to 3.6% (11/307) by UV lights (both p < 0.03 compared with the control group). Time-to-event analysis demonstrated that TB infection was prevented by ionizers (log-rank 27; p < 0.0001) and by UV lights (log-rank 46; p < 0.0001). Time-to-event analysis also demonstrated that TB disease was prevented by ionizers (log-rank 3.7; p = 0.055) and by UV lights (log-rank 5.4; p = 0.02). An alternative analysis using an airborne infection model demonstrated that ionizers prevented 60% of TB infection and 51% of TB disease, and that UV lights prevented 70% of TB infection and 54% of TB disease. In all analysis strategies, UV lights tended to be more protective than ionizers.ConclusionsUpper-room UV lights and negative air ionization each prevented most airborne TB transmission detectable by guinea pig air sampling. Provided there is adequate mixing of room air, upper-room UV light is an effective, low-cost intervention for use in TB infection control in high-risk clinical settings.

Electrostatic charging of particles in enclosed spaces has been shown to be an effective means of reducing airborne dust. Dust generated during the hatching process has been strongly implicated in Salmonella transmission, which complicates the cleaning and disinfecting processes for hatchers. Following two preliminary trials in which dust reduction was measured, four trials were conducted to evaluate the effectiveness of an electrostatic space charge system (ESCS) on the levels of total aerobic bacteria (TPC), enterobacteriaceae (ENT), and Salmonella within an experimental hatching cabinet. The ESCS was placed in a hatching cabinet that was approximately 50% full of 18-d-old broiler hatching eggs. The ESCS operated continuously to generate a strong negative electrostatic charge throughout the cabinet through hatching, and dust was collected in grounded trays containing water and a degreaser. An adjacent hatching cabinet served as an untreated control. Air samples from hatchers were collected daily, and sample chicks from each hatcher were grown out to 7 d of age for cecal analysis in three of the trials. The ESCS significantly (P < 0.05) reduced TPC and ENT by 85 to 93%. Dust concentration was significantly reduced (P < 0.0001) during the preliminary trials with an average reduction of 93.6%. The number of Salmonella per gram of cecal contents in birds grown to 7 d of age was significantly (P < 0.001) reduced by an average log10 3.4 cfu/g. This ionization technology is relatively inexpensive and could be used to reduce airborne bacteria and dust within the hatching cabinet.

Salmonella enteritidis is currently thought to be transmitted principally through contact with infected individuals and ingestion of fecally contaminated materials. The present study was undertaken to determine if S. enteritidis could be spread in chickens by the airborne route and if induced molting could affect this mode of transmission. To test for airborne transmission, hens were placed in two rows of cages, the rows separated from each other by 1 m. One row of hens was challenged with S. enteritidis, whereas the other row remained unchallenged but exposed to the room air. Ventilation delivered within the room provided an even air distribution within the area and minimized directional air flow toward any set of cages. In Expt. 1, 4 of 12 and 9 to 12 exposed molted hens became infected with S. enteritidis after 3 and 8 days of exposure, respectively, compared with 1 of 12 and 0 of 12 unmolted hens sampled on the same days. Similar S. enteritidis levels were detected circulating in the air in the two rooms housing the hens. Expts. 2 and 3 examined airborne transmission in molted hens only. In Expt. 2, 2 of 12 exposed hens became infected with S. enteritidis at 3 days postchallenge, and this increased to 12 of 12.1 wk later. In Expt. 3, exposed hens were again housed in cages 1 m from challenged hens but were placed in every other cage to prevent transmission through contact with hens in adjacent cages. At day 3 post challenge, 0 of 12 exposed hens were culture positive for S. enteritidis, and this increased to only 3 of 10 positive hens at day 10. Large numbers of S. enteritidis shed by the molted challenged hens were recovered from the floors beneath the cages. These results indicated that, contrary to the generally held beliefs regarding organism spread, airborne transmission of S. enteritidis can occur and induced molting can provide the impetus for this event. As was observed previously, rapid dissemination of the organism to other members of the flock resulted through bird-to-bird contact.

Airborne dust in poultry housing is known to be one of the primary means by which disease-causing organisms are spread throughout a house. An electrostatic space charge system (ESCS) was used to reduce airborne dust in a small-scale broiler breeder house. The system used ceiling fans to distribute negatively charged air throughout the room and to move negatively charged dust downward toward the grounded litter where most of it would be captured. The system significantly (P < 0.0001) reduced airborne dust by an average of 61%, ammonia by an average of 56% (P < 0.0001), and airborne bacteria by 67% (P < 0.0001). Earlier studies with an ESCS have resulted in significant reductions of airborne dust, bacteria, and airborne transmission of disease in poultry hatching cabinets, caged layer rooms, and in controlled environment disease transmission cabinets. The ESCS was shown to be a reliable and easily maintained system for reducing airborne dust, ammonia, and bacteria in a small broiler breeder house. Results of this study combined with the results of related ESCS studies suggest that the system could probably be scaled up to full-sized production houses for poultry or other animals for dust reduction, pathogen reduction, and possibly ammonia reduction. All of the applications have potential for improving human health as well as animal health.

Although direct contact with infected birds and indirect contact with contaminated environmental surfaces are known to be important factors in the dissemination of Salmonella enteritidis in poultry flocks, the potential role of airborne transmission is less clearly defined. This study considered the mechanism by which S. enteritidis might spread between groups of chicks housed in controlled-environment disease transmission cabinets, separated by an unoccupied space that prevented any direct or indirect contact. Airflow in these cabinets was directed across the unoccupied area from one ("upstream") group of chicks to the other ("downstream") group. In each of four replicate trials, two groups of 25 chicks were placed in the upstream ends of transmission cabinets and orally inoculated with S. enteritidis at 1 week of age. One day later, 25 1-day-old chicks were placed in the downstream end of each cabinet. When chicks were removed and sampled at 3 and 7 days postinoculation, S. enteritidis was found on the feathers of 77% of the downstream chicks. Moreover, 33% of the downstream chicks became infected with S. interitidis. The comparative frequencies of recovery of S. enteritidis from various downstream sampling sites suggested that infection was apparently transmitted principally by oral ingestion, perhaps from environmental surfaces contaminated by airborne movement of the pathogen. Reducing the airborne movement of S. enteritidis in poultry houses should thus help limit the spread of infection within flocks and thereby diminish the incidence of production of contaminated eggs.

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Inactivated oil-emulsion (OE) Newcastle disease (ND) and avian influenza (AI) vaccines were injected into 18-day-old white rock (WR) and white leghorn (WL) chicken embryos to evaluate their immunologic efficacy and their effects on hatchability. Embryonating eggs were inoculated at 1.5 inches depth with various vaccine volumes and antigen concentrations. Serum hemagglutination-inhibition (HI) titers were first detected in chickens at 2 wk posthatch. Protection against morbidity and mortality was demonstrated in all of 10 chickens vaccinated as embryos and challenged with viscerotropic velogenic ND virus at 53 days of age and also in all of eight in ovo- vaccinated chickens challenged with highly pathogenic AI virus at 34 days of age. All of five unvaccinated control chickens for each respective ND- and AI-vaccinated group died. In pooled groups from successive hatches, the hatchability of WR or WL embryos injected with 100 microliters of vaccine was not significantly different (P > 0.05) from unvaccinated hatchmate controls when needle gauges of 22, 20, and 18 were used. Seroconversion rates of chickens vaccinated as embryos ranged from 27% to 100% with ND vaccination and 85% to 100% for AI vaccination. For ND, geometric mean HI titers of chickens per vaccine group ranged from 11 to 733, and in pooled groups, the range was 49 to 531. Titers for AI vaccine groups ranged from 156 to 1178. This study demonstrated that acceptable hatchability, seroconversion rates, and protective immunity can be attained with in ovo inoculation of ND or AI OE vaccines if the vaccines are prepared with sufficient antigen and administered properly.

Four-week-old mixed-sex White Rock chickens were used in four experiments to determine the effect of negative air ion enrichment on airborne transmission of the Roakin strain of Newcastle disease virus (NDV). The experiments were conducted in specially constructed airborne disease transmission cabinets in which donor (upwind) chickens cannot contact susceptible (downwind) chickens because of physical separation by a "no man's land." Temperature and humidity were computer-controlled at 26.7 C and 50% relative humidity, and ventilation rates were manually adjusted from 0.34 to 1.36 m3/min (12 to 48 ft3/min). Donor chickens were inoculated with Roakin NDV by eyedrop and intranasal routes and placed in the upwind end of each cabinet. One day later, susceptible chickens were placed in the downwind end. Seroconversion (> or = 1:10 NDV hemagglutination-inhibition titer) was considered evidence of infection from inoculation (upwind) or airborne transmission (downwind). Commercial air ion generators were used either in the ends or in the "no man's land" of the treatment cabinets and operated at power supply voltages ranging from -8kV direct current to -15 kV direct current. The use of negative air ion generators reduced airborne transmission an average of 6.6% to 27.7% compared with the control cabinets. Significant (P < or = 0.05) reductions in transmission were obtained with some treatments. The greatest reduction in transmission was obtained with the higher power supply voltages (13.8% reduction) and when the ionizers were placed in the "no man's land" (27.7% reduction) between the upwind and downwind chickens.