Invasive mammalian predators habituate to and generalize avian prey cues: a mechanism for conserving native prey.

Invasive mammalian predators can cause the decline and extinction of vulnerable native species. Many invasive mammalian predators are dietary generalists that hunt a variety of prey. These predators often rely upon olfaction when foraging, particularly at night. Little is understood about how prey odor cues are used to inform foraging decisions. Prey cues can vary spatially and temporally in their association with prey and can either reveal the location of prey or lead to unsuccessful foraging. Here we examine how two wild-caught invasive mammalian bird predator species (European hedgehogs Erinaceus europaeus and ferrets Mustela putorius furo) respond to unrewarded bird odors over successive exposures, first demonstrating that the odors are perceptually different using house mice (Mus musculus) as a biological olfactometer. We aim to test if introduced predators categorize odor cues of similar prey together, a tactic that could increase foraging efficiency. We exposed house mice to the odors using a standard habituation/dishabituation test in a laboratory setting, and wild-caught European hedgehogs and ferrets in an outdoor enclosure using a similar procedure. Mice discriminated among all bird odors presented, showing more interest in chicken odor than quail or gull odor. Both predator species showed a decline in interest toward unrewarded prey odor (i.e., habituation), but only ferrets generalized their response from one unrewarded bird odor to another bird odor. Hedgehog responses to unrewarded bird odors were highly variable between individuals. Taken together, our results reveal interspecific and intraspecific differences in response to prey odors, which we argue are a consequence of different diet breadth, life and evolutionary histories, and the conditions in each experiment. Generalization of prey odors may have enabled some species of invasive predators to efficiently hunt a range of intraguild prey species, for example, ground-nesting shorebirds. Olfactory manipulation of predators may be a useful conservation tool for threatened prey if it reduces the conspicuousness of vulnerable prey.

Modeling habituation of introduced predators to unrewarding bird odors for conservation of ground-nesting shorebirds.

Foraging mammalian predators face a myriad of odors from potential prey. To be efficient, they must focus on rewarding odors while ignoring consistently unrewarding ones. This may be exploited as a nonlethal conservation tool if predators can be deceived into ignoring odors of vulnerable secondary prey. To explore critical design components and assess the potential gains to prey survival of this technique, we created an individual-based model that simulated the hunting behavior of three introduced mammalian predators on one of their secondary prey (a migratory shorebird) in the South Island of New Zealand. Within this model, we heuristically assessed the outcome of habituating the predators to human-deployed unrewarding bird odors before the bird's arrival at their breeding grounds, i.e., the predators were "primed." Using known home range sizes and probabilities of predators interacting with food lures, our model suggests that wide-ranging predators should encounter a relatively large number of odor points (between 10 and 115) during 27 d of priming when odor is deployed within high-resolution grids (100-150 m). Using this information, we then modeled the effect of different habituation curves (exponential and sigmoidal) on the probability of predators depredating shorebird nests. Our results show that important gains in nest survival can be achieved regardless of the shape of the habituation curve, but particularly if predators are fast olfactory learners (exponential curve), and even if some level of dishabituation occurs after prey become available. Predictions from our model can inform the amount and pattern in which olfactory stimuli need to be deployed in the field to optimize encounters by predators, and the relative gains that can be expected from reduced predation pressure on secondary prey under different scenarios of predator learning. Habituating predators to odors of threatened secondary prey may have particular efficacy as a conservation tool in areas where lethal predator control is not possible or ethical, or where even low predator densities can be detrimental to prey survival. Our approach is also relevant for determining interaction probabilities for devices other than odor points, such as bait stations and camera traps.

Spatiotemporal interactions between wild boar and cattle: implications for cross-species disease transmission.

Controlling infectious diseases at the wildlife/livestock interface is often difficult because the ecological processes driving transmission between wildlife reservoirs and sympatric livestock populations are poorly understood. Thus, assessing how animals use their environment and how this affects interspecific interactions is an important factor in determining the local risk for disease transmission and maintenance. We used data from concurrently monitored GPS-collared domestic cattle and wild boar (Sus scrofa) to assess spatiotemporal interactions and associated implications for bovine tuberculosis (TB) transmission in a complex ecological and epidemiological system, Doñana National Park (DNP, South Spain). We found that fine-scale spatial overlap of cattle and wild boar was seasonally high in some habitats. In general, spatial interactions between the two species were highest in the marsh-shrub ecotone and at permanent water sources, whereas shrub-woodlands and seasonal grass-marshlands were areas with lower predicted relative interactions. Wild boar and cattle generally used different resources during winter and spring in DNP. Conversely, limited differences in resource selection during summer and autumn, when food and water availability were limiting, resulted in negligible spatial segregation and thus probably high encounter rates. The spatial gradient in potential overlap between the two species across DNP corresponded well with the spatial variation in the observed incidence of TB in cattle and prevalence of TB in wild boar. We suggest that the marsh-shrub ecotone and permanent water sources act as important points of TB transmission in our system, particularly during summer and autumn. Targeted management actions are suggested to reduce potential interactions between cattle and wild boar in order to prevent disease transmission and design effective control strategies.

Comparison of ranging behaviour in a multi-species complex of free-ranging hosts of bovine tuberculosis in relation to their use as disease sentinels.

Sentinel species are increasingly used by disease managers to detect and monitor the prevalence of zoonotic diseases in wildlife populations. Characterizing home-range movements of sentinel hosts is thus important for developing improved disease surveillance methods, especially in systems where multiple host species co-exist. We studied ranging activity of major hosts of bovine tuberculosis (TB) in an upland habitat of New Zealand: we compared home-range coverage by ferrets (Mustela furo), wild deer (Cervus elaphus), feral pigs (Sus scrofa), brushtail possums (Trichosurus vulpecula) and free-ranging farmed cattle (Bos taurus). We also report in detail the proportional utilization of a seasonal (4-monthly) range area for the latter four species. Possums covered the smallest home range (<30 ha), ferrets covered ~100 ha, pigs ~4 km(2), deer and cattle both >30 km2. For any given weekly period, cattle, deer and pigs were shown to utilize 37­45% of their estimated 4-month range, while possums utilized 62% during any weekly period and 85% during any monthly period of their estimated 4-month range. We suggest that present means for estimating TB detection kernels, based on long-term range size estimates for possums and sentinel species, probably overstate the true local surveillance coverage per individual.

Detection parameters for managing invasive rats in urban environments.

Effective mitigation of the impacts of invasive ship rats (Rattus rattus) requires a good understanding of their ecology, but this knowledge is very sparse for urban and peri-urban areas. We radiomarked ship rats in Wellington, New Zealand, to estimate detection parameters (σ, ε0, θ, and g0) that describe the process of an animal encountering a device (bait stations, chew cards and WaxTags) from a distance, and then approaching it and deciding whether to interact with it. We used this information in simulation models to estimate optimal device spacing for eradicating ship rats from Wellington, and for confirming eradication. Mean σ was 25.37 m (SD = 11.63), which equates to a circular home range of 1.21 ha. The mean nightly probability of an individual encountering a device at its home range center (ε0) was 0.38 (SD = 0.11), whereas the probability of interacting with the encountered device (θ) was 0.34 (SD = 0.12). The derived mean nightly probability of an individual interacting with a device at its home range center (g0) was 0.13 (SD = 0.08). Importantly, σ and g0 are intrinsically linked through a negative relationship, thus g0 should be derived from σ using a predictive model including individual variability. Simulations using this approach showed that bait stations deployed for about 500 days using a 25 m × 25 m grid consistently achieved eradication, and that a surveillance network of 3.25 chew cards ha-1 or 3.75 WaxTags ha-1 active for 14 nights would be required to confidently declare eradication. This density could be halved if the surveillance network was deployed for 28 nights or if the prior confidence in eradication was high (0.85). These recommendations take no account of differences in detection parameters between habitats. Therefore, if surveillance suggests that individuals are not encountering devices in certain habitats, device density should be adaptively revised. This approach applies to initiatives globally that aim to optimise eradication with limited funding.

Misinformation tactics protect rare birds from problem predators.

Efficient decision-making integrates previous experience with new information. Tactical use of misinformation can alter choice in humans. Whether misinformation affects decision-making in other free-living species, including problem species, is unknown. Here, we show that sensory misinformation tactics can reduce the impacts of predators on vulnerable bird populations as effectively as lethal control. We repeatedly exposed invasive mammalian predators to unprofitable bird odors for 5 weeks before native shorebirds arrived for nesting and for 8 weeks thereafter. Chick production increased 1.7-fold at odor-treated sites over 25 to 35 days, with doubled or tripled odds of successful hatching, resulting in a 127% increase in modeled population size in 25 years. We demonstrate that decision-making processes that respond to changes in information reliability are vulnerable to tactical manipulation by misinformation. Altering perceptions of prey availability offers an innovative, nonlethal approach to managing problem predators and improving conservation outcomes for threatened species.

The LeVe CPAP System for Oxygen-Efficient CPAP Respiratory Support: Development and Pilot Evaluation.

Background: The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has placed a significant demand on healthcare providers (HCPs) to provide respiratory support for patients with moderate to severe symptoms. Continuous Positive Airway Pressure (CPAP) non-invasive ventilation can help patients with moderate symptoms to avoid the need for invasive ventilation in intensive care. However, existing CPAP systems can be complex (and thus expensive) or require high levels of oxygen, limiting their use in resource-stretched environments. Technical Development + Testing: The LeVe ("Light") CPAP system was developed using principles of frugal innovation to produce a solution of low complexity and high resource efficiency. The LeVe system exploits the air flow dynamics of electric fan blowers which are inherently suited to delivery of positive pressure at appropriate flow rates for CPAP. Laboratory evaluation demonstrated that performance of the LeVe system was equivalent to other commercially available systems used to deliver CPAP, achieving a 10 cm H2O target pressure within 2.4% RMS error and 50-70% FiO2 dependent with 10 L/min oxygen from a commercial concentrator. Pilot Evaluation: The LeVe CPAP system was tested to evaluate safety and acceptability in a group of ten healthy volunteers at Mengo Hospital in Kampala, Uganda. The study demonstrated that the system can be used safely without inducing hypoxia or hypercapnia and that its use was well-tolerated by users, with no adverse events reported. Conclusions: To provide respiratory support for the high patient numbers associated with the COVID-19 pandemic, healthcare providers require resource efficient solutions. We have shown that this can be achieved through frugal engineering of a CPAP ventilation system, in a system which is safe for use and well-tolerated in healthy volunteers. This approach may also benefit other respiratory conditions which often go unaddressed in Low and Middle Income Countries (LMICs) for want of context-appropriate technology designed for the limited oxygen resources available.

Determinants of undernutrition in rural communities of a protected area in Gabon.

OBJECTIVE: To understand how access to natural resources may contribute to nutrition. DESIGN: In each of the two major seasons, data were collected during a 7 d period using observations, semi-structured interviews, anthropometric measures and a weighed food consumption survey. SETTING: Four rural communities selected to represent inland and coastal areas of the Gamba Complex in Gabon. SUBJECTS: In each community, all individuals from groups vulnerable to malnutrition, i.e. children aged 0-23 months (n 41) and 24-59 months (n 63) and the elderly (n 101), as well as women caregivers (n 96). RESULTS: In most groups, household access to natural resources was associated with household access to food but not with individual nutritional status. In children aged 0-23 months, access to care and to health services and a healthy environment were the best predictors of length-for-age (adjusted R2: 14%). Health status was the only predictor of weight-for-height in children aged 24-59 months (adjusted R2: 14%). In women caregivers, household food security was negatively associated with nutritional status, as was being younger than 20 years (adjusted R2: 16%). Among the elderly, only nutrient adequacy predicted nutritional status (adjusted R2: 5%). CONCLUSION: Improving access to care and health for young children would help reverse the process of undernutrition. Reaching a better understanding of how the access of individuals to both food and other resources relate to household access could further our appreciation of the constraints to good nutrition. This is particularly relevant in women to ensure that their possibly important contribution to the household is not at their own expense.

Nutritional status and dietary adequacy in rural communities of a protected area in Gabon.

OBJECTIVE: As part of a larger study designed to understand how to protect the food and nutrition security of individuals living in a protected area of Gabon, we assessed their nutritional status and its relationship to dietary adequacy and health status. DESIGN: A 7 d food consumption survey was conducted during each of the two major seasons using a weighing method. Data were also collected on weight, height and health of individuals as well as on sociodemographic characteristics and potential determinants of the nutrition situation. SETTING: Four rural communities were intentionally selected to represent both inland and coastal settings and access to food markets. SUBJECTS: Approximately 500 individuals representing over 90% of the population of these communities participated in the survey during each season. RESULTS: Undernutrition was present in the area, particularly among children <5 years of age and the elderly. Health was generally good and under-fives were most frequently ill. Energy, Fe and vitamin A requirements of individuals were generally not satisfied; the opposite was true for protein. The estimated prevalence of inadequate intakes of energy and vitamin A was very high in most age groups. Global nutrient adequacy was associated with nutritional outcome. CONCLUSIONS: Individuals do not eat enough and breast-feeding practices are poor. Many suffer from undernutrition, particularly young children and the elderly. The results confirm the need to investigate the determinants of this poor nutrition situation to ensure that protection of natural resources will not be associated with harm to the well-being of the population.

Proliferation-dependent topoisomerase II content as a determinant of antineoplastic drug action in human, mouse, and Chinese hamster ovary cells.

We have shown previously that quiescent Chinese hamster ovary (CHO) cells are less sensitive than log phase CHO cells to the cytotoxic and DNA cleavage effects of etoposide, a drug which appears to act via DNA topoisomerase II. This loss of sensitivity was associated with a decrease in topoisomerase enzyme activity in nuclear extracts of the quiescent cells. We have now extended our observations by examining the basis for the reduction in enzyme activity during quiescence. DNA topoisomerase II content, as assayed by immunoblotting with a polyclonal rabbit anti-topoisomerase II antiserum, was virtually absent in nuclear extracts of quiescent CHO cells in contrast to logarithmically growing cells. This suggests that the previously demonstrated loss of enzyme activity in CHO cells is a function of reduction in content rather than posttranslational modifications of the enzyme. Quiescent human lymphoblastic CCRF cells also exhibited reduced topoisomerase II content compared to actively proliferating cultures, but the difference was less than that observed in CHO cells. In contrast, log and plateau phase cultures of mouse leukemia L1210 cells exhibited similar topoisomerase II content. Reduction in enzyme content correlated with the ability of these cell lines to accumulate during quiescence with a G0-G1 content of DNA. Sensitivity to the DNA cleavage effects of etoposide in dividing and nondividing cells correlated well with enzyme content. As has been observed with CHO cells, both CCRF and L1210 cells in plateau phase were more resistant to the cytotoxic effects of etoposide than those actively dividing. The result with L1210 cells was surprising, however, in light of the equivalent DNA damage observed under the two growth conditions. Our data indicate that topoisomerase II enzyme content is proliferation dependent in some but not all cells and suggest that while enzyme content may be important in drug resistance in some cell types, other factors can decrease the sensitivity of the cell to cleavable complex formation as well.

Attenuated topoisomerase II content directly correlates with a low level of drug resistance in a Chinese hamster ovary cell line.

A new multiple drug-resistant Chinese hamster ovary cell line, CHO-SMR5, has been isolated which demonstrates a direct correlation between reduced cellular topoisomerase II activity (5-fold reduction) and a low level of resistance (3- to 7-fold) to topoisomerase II inhibitors. This cell line, initially selected for resistance to 9-(4,6-O-ethylidene-beta-D-glucopyranosyl)-4'-demethylepipodophylloto xin, exhibits cross-resistance to other topoisomerase II inhibitors including 4'-(9-acridinylamino)methanesulfon-m-anisidide, doxorubicin, and mitoxantrone. The resistant cells show a 4.5-fold decrease in topoisomerase II by immunoblotting when compared to wild-type cells. Drug uptake studies reveal equivalent equilibrium intracellular concentrations of [3H]9-(4,6-O-ethylidene-beta-D-glucopyranosyl)-4'-demethyepipodophyll otoxin in the resistant and parental cells. The catalytic activity of topoisomerase II (decatenation of kinetoplast DNA) is 5-fold less in the drug-resistant cell line relative to wild-type Chinese hamster ovary cells. Drug-induced DNA damage, measured as either formation of DNA double-strand breaks or covalent DNA-enzyme complexes, is 4-fold less in the resistant cell line. Finally, Northern blot analysis demonstrates a 5-fold reduction in topoisomerase II mRNA isolated from log phase CHO-SMR5 cells. These findings suggest that a reduced level of topoisomerase II is likely to be the sole mechanism of drug resistance in this novel cell line.

Refining Operational Practice for Controlling Introduced European Rabbits on Agricultural Lands in New Zealand.

European rabbits (Oryctolagus cuniculus) pose a major threat to agricultural production and conservation values in several countries. In New Zealand, population control via poisoning is a frontline method for limiting rabbit damage, with large areas commonly treated using the metabolic toxin sodium fluoroacetate ('1080') delivered in bait via aerial dispersal. However, this method is expensive and the high application rates of the active ingredient cause public antipathy towards it. To guide reductions in cost and toxin usage, we evaluated the economics and efficacy of rabbit control using an experimental approach of sowing 1080-bait in strips instead of the commonly-used broadcast sowing method (i.e. complete coverage). Over a 4-year period we studied aerial delivery of 0.02% 1080 on diced carrot bait over ~3500 ha of rabbit-prone land in the North and South islands. In each case, experimental sowing via strip patterns using 10-15 kg of bait per hectare was compared with the current best practice of aerial broadcast sowing at 30-35 kg/ha. Operational kill rates exceeded 87% in all but one case and averaged 93-94% across a total of 19 treatment replicates under comparable conditions; there was no statistical difference in overall efficacy observed between the two sowing methods. We project that strip-sowing could reduce by two thirds the amount of active 1080 applied per hectare in aerial control operations against rabbits, both reducing the non-target poisoning risk and promoting cost savings to farming operations. These results indicate that, similarly to the recently-highlighted benefits of adopting strip-sowing for poison control of introduced brushtail possums (Trichosurus vulpecula) in New Zealand, aerial strip-sowing of toxic bait could also be considered a best practice method for rabbit control in pest control policy.

Quantifying short-term foraging movements in a marsupial pest to improve targeted lethal control and disease surveillance.

In New Zealand, the introduced marsupial brushtail possum (Trichosurus vulpecula) is a pest species subject to control measures, primarily to limit its ability to transmit bovine tuberculosis (TB) to livestock and for conservation protection. To better define parameters for targeted possum control and TB surveillance, we here applied a novel approach to analyzing GPS data obtained from 44 possums fitted with radio-tracking collars, producing estimates of the animals' short-term nocturnal foraging patterns based on 1-, 3- or 5-nights' contiguous data. Studies were conducted within two semi-arid montane regions of New Zealand's South Island High Country: these regions support low-density possum populations (<2 possums/ha) in which the animals' home ranges are on average larger than in high-density populations in forested habitat. Possum foraging range width (FRW) estimates increased with increasing monitoring periods, from 150-200 m based on a single night's movement data to 300-400 m based on 5 nights' data. The largest average FRW estimates were recorded in winter and spring, and the smallest in summer. The results suggest that traps or poison-bait stations (for lethal control) or monitoring devices (for TB surveillance), set for > 3 consecutive nights at 150 m interval spacings, would likely place >95% of the possums in this type of habitat at risk of encountering these devices, year-round. Modelling control efficacy against operational expenditure, based on these estimations, identified the relative cost-effectiveness of various strategies that could be applied to a typical aerial poisoning operation, to reduce the ongoing TB vectorial risk that possums pose in the High Country regions. These habitat-specific findings are likely to be more relevant than the conventional pest control and monitoring methodologies developed for possums in their more typical forested habitat.

The use of changes in hair root morphology in the assessment of protein-calorie malnutrition.

A study was carried out to evaluate the use of changes in hair root morphology in the assessment of protein-calorie malnutrition (PCM) among a group of Black West Indian children. Significant differences in mean shaft diameter, mean % anagen, and mean % telogen were found only between the well-nourished and the severely malnourished groups. No significant differences in mean % atrophy, and in mean diameter of anagen bulbs were found among well-nourished children, children with mild-moderate PCM, severely malnourished children, and children hospitalized for conditions with a secondary effect on nutritional status. The method was found to be time consuming; it can be used only for differentiating well-nourished from severely malnourished children; and it cannot be used for determining the prevalence of the different degrees of PCM. For these reasons, the method is not recommended for use in the field assessment of PCM.

Lactose malabsorption among Masai children of East Africa.

There is much disagreement about milk and its use in feeding programs both in the United States and internationally. A few authors suggest that milk consumption should not be encouraged in lactose intolerant populations due to adverse symptoms. Others suggest, however, that small or modest quantities of milk can be tolerated and can be nutritionally useful to such groups. Data are presented in this paper that show that 1) the Masai regularly drink considerable quantities of milk without apparent symptoms, 2) milk is an important constituent of the Masai diet, and 3) 62% of 21 Masai examined were malabsorbers of lactose as measured by the lactose tolerance test. This finding of lactose malabsorption in a nomadic cattle raising and milk drinking people is interesting and is contrary to the views often expressed by anthropologists and others. An ability to drink nutritionally useful quantities of milk does not, however, necessarily mean that milk production or imports should be encouraged in the Lesser Developed Countries.

Rapid and portable methods of lactose tolerance test administration.

Abbreviated, portable methods of lactose tolerance test administration were investigated. Results obtained with the Ames Reflectance Meter/Dextrostix system for blood glucose determination during lactose tolerance testing were compared with those obtained from a standard method, the AutoAnalyzer. Subjects who had maximum blood glucose rises below 20 mg/100 ml were considered to have a flat lactose tolerance curve and were designated lactose nondigesters. Results of the two methods were very similar for determination of maximum rise in blood sugar over fasting level, for obtaining values of individual blood sugar determinations, and for diagnosis of lactose nondigesters. The effect of omission of the final blood sample on tolerance test results was examined. It was found that maximum rises in blood glucose occurred before the final sample in 31 of 35 cases on the AutoAnalyzer and in 26 of 27 cases on the Reflectance Meter. In no case did omission of the final sample change the results of the lactose tolerance test.

Anemia of pregnancy in Liberia, West Africa: a therapeutic trial.

Research was conducted in Liberia, West Africa to ascertain which hematinics produce the best Hb response in women during the 3rd trimester of pregnancy. After obtaining background information, each of the 621 subjects was randomly assigned to one of four treatment groups. Group 1 was given 60 mg iron once daily, group 2 was given 60 mg iron 3 times daily, group 3 was given 60 mg iron 3 times daily plus a 5-mg folic acid tablet once daily, and group 4 was given the same treatment as group 3 but also a weekly antimalarial prophylactic. For comparison, 58 untreated women in their 3rd trimester were also studied. Before therapy the five groups were similar with respect to selected socioeconomic status, health, and dietary variables. Hb response to therapy was measured at 4-wk intervals from the 24th wk of gestation until term. The Hb rises in all four treatment groups were significantly (p less than 0.001) higher than the base-line values at 4, 8, and 12 wk after the interventions. The percentage of anemic women was reduced from 78 to 45% over the 12 wk of supplementation. Hb rises in groups 3 and 4 were not significantly different from those in groups receiving iron alone. It is concluded that iron deficiency is the main cause of anemia in this population.

An evaluation of strategies to control vitamin A deficiency in the Philippines.

Xerophthalmia has been found to be an important cause of blindness in the Philippines. An earlier study had investigated its prevalence and epidemiology on the island of Cebu. The research now presented consists of an evaluation of the relative effectiveness of three different intervention strategies to control vitamin A deficiency in Cebu. These interventions were 1) a public health and horticulture intervention, 2) the provision of 200,000 IU of vitamin A to children every 6 months (the "capsule intervention"), and 3) the fortification of monosodium glutamate with vitamin A. A total of 12 areas or barangays were included. Each intervention was monitored in four different barangays, two urban and two rural, for almost 2 years. Similar examinations were performed before and after the interventions. The monosodium glutamate fortification was the only intervention that resulted both in a significant reduction in clinical signs of xerophthalmia and in a significant rise in serum vitamin A levels. Fortification is now being planned in three Philippine provinces.

Vitamin A supplementation and morbidity among preschool children in south India.

A randomized, double-blind, placebo-controlled trial was conducted in an ongoing Growth Monitoring Research project in TamilNadu, India, to assess the impact of high-dose vitamin A supplementation on morbidity among mildly to moderately malnourished children aged < 3 y. Every 4 mo, the treatment group received 60 mg vitamin A (200,000 IU) whereas the control group received a placebo. Cases of xerophthalmia and severe malnutrition were excluded. Anthropometric measurements and serum retinol determinations were made at baseline and at the end of 1 y. Morbidity data were collected by trained village-level workers throughout the study period by using the weekly recall method. The two groups had similar nutritional status, serum retinol concentrations, age-sex composition, and other sociodemographic indicators at baseline. The mean number of episodes per child-year was 2.62 +/- 2.95 and 2.56 +/- 2.5 for respiratory illness and 1.9 +/- 2.2 and 1.77 +/- 1.77 for diarrhea for the vitamin A (n = 309) and placebo (n = 274) groups, respectively. The differences in respiratory and diarrheal morbidity between the two groups were not statistically significant and these findings remained unaltered after multivariate analysis in which the effects of age, sex, socioeconomic status, sanitation, etc, were considered. These findings are similar to other recent findings and indicate that vitamin A supplementation does not reduce common morbidity in children with mild-to-moderate vitamin A deficiency in areas where access to health care and immunization are good.