Lloyd A. Selby

A tobacco related epidemic of congenital limb deformities in swine

Abstract An epidemic of congenital limb deformities in swine is described. The epidemic occurred among 79 Duroc sows and gilts on a farm in Howard County, Missouri, during the period September 11, 1967, to March 3, 1968. The 79 females farrowed 782 pigs: 742 (95%) were born alive, 40 (5%) were born dead, and 59 (7.5%) were born with congenital abnormalities. The abnormal pigs were farrowed by 14 sows. These sows farrowed 149 pigs and 59 (40%) were abnormal. Tobacco stalks were placed in a swine lot and pasture between October 25, 1967, and December 7, 1967, and some of the sows were observed eating the stalks. On December 7, 1967, four sows had an illness which lasted 24–48 hours. The first 38 days of pregnancies in those sows with the affected progeny occurred during the time when the tobacco was available to them. Other animals not exposed to the tobacco stalks as a food source had no birth defects. The animals involved in the epidemic during prior and later reproductive periods had no abnormalities in their litters. The tobacco stalks, therefore, appeared to have some association with the epidemic. The tobacco stalks were tested for nitrate-nitrogen, pesticides, fungi, nicotine, and maleic hydrazide. The nitrate-nitrogen varied from 20 to 1390 ppm, and no significant amounts of aldrin, dieldrin, or pp′ -DDT were found. The fungi consistently isolated included a species of Penicillium identified as a variant of Penicillium cyclopium . Other species of fungi were isolated only sporadically, and no Aspergilli were found. Nicotine, other alkaloids or components of the tobacco stalks, appeared to be the most likely cause of the epidemic. The tobacco stalks eaten by the swine contained 1058 ppm of nicotine and 115 ppm of maleic hydrazide. The possible relationship of this epidemic of birth defects in swine associated with the ingestion of tobacco stalks to the increased fetal loss described among smoking mothers is discussed.

Outbreak of swine malformations associated with the wild black cherry, Prunus serotina.

An outbreak of congenital malformations in swine occurred in Warren County, Missouri, during the late spring and summer of 1968. Sows which farrowed malformed offspring were bred and spent their gestation cycle in one pasture. Sows in an adjacent pasture bred by the same boar during the same period, farrowed only normal offspring. Field observation and epidemiologic studies indicate that the cause of the malformations was environmental in nature rather than hereditary. A comparison of the critical time period of exposure and environmental factors suggest an association between the malformations and consumption of wild black cherries (Prunus serotina) by the pregnant sows. Other environmental factors which might have contributed to the cause of the outbreak are discussed.

Antagonistic effect of zinc on increased urine δ-aminolevulinic acid excretion in lead-intoxicated rats

Abstract Urine δ-aminolevulinic acid (ALAU) excretion has previously been reported as being closely correlated with the clinical picture of lead poisoning. In the present investigation, rats were administered either zinc or lead or both. Zinc administration resulted in the reduction to near normal levels of ALAU excretion in lead-intoxicated rats. This effect occurred in the absence of any significant reduction in blood lead levels or any alleviation of the anemia of lead toxicity. The observations place considerable doubt on the validity of using ALAU screening tests as a means of determining lead exposure.

A Survey of Swine Production Health Problems and Health Maintenance Expenditures

Abstract Swine producers in the Missouri Mail-In-Record program provided information on herd health problems, death losses and health maintenance expenditures in their swine herd for the years 1978 and 1979. Swine health problems and death losses dampen profits for swine producers. During the study period approximately one-third of all pigs raised by Missouri Mail-In-Record swine panel producers were affected by health problems. It is important for swine producers to keep health problems under control. Important health problems for swine producers were scours, pneumonia, salmonellosis, TGE, and influenza. Important death causal factors were crushing or trauma, scours, lack of milk, and pneumonia. Health problems and death losses were most severe during the first quarter of the year. The major swine health expenditure was for services which were farmer administered. On a relative basis smaller producers depended more on veterinarians for seervices than did larger producers. Also, producers that had more than one type of production technology (pasture, confinement, etc.) tended to have larger animal health expenditure levels.

The association of selected climatic factors with natural alimentary parasites of the dog.

In an effort to define the effects of the natural climate on the infection rates of canine alimentary parasites, a fecal flotation examination for alimentary parasites was performed on 2093 domesticated dogs during a 15-month period at Fort Leonard Wood, Missouri. Concurrently, 15 climatic variables were collected for comparison with the frequency of parasitism. The frequency of natural mono- and multi-infections with coccidia (Isospora spp.), ascarids (Toxocara canis and Toxascaris leonina), hookworms (Ancylostoma caninum), and whipworms (Trichuris vulpis) was determined and used to evaluate the randomness of multi-infections. In comparing parasitisms with the climatic factors, a complex bioclimatic relationship was found. The relationship was dependent on the parasitic agent(s) and the relative time frame. Natural climatic conditions influenced the ability of Isospora spp. to multi-infect hosts and strongly influenced the infection rate of Ancylostoma caninum. The study suggests that there is a bioclimatic interaction involving both the canine host and the parasites extra-host life stages.

Effects of swine husbandry on the incidence of congenital malformations: a matched-paired study☆

Abstract One hundred case-control herds were evaluated to determine the possible association between congenital malformations and husbandry practices in two subpopulations of Missouri swine. The etiology of the malformations in these populations was thought to be primarily environmental. General geographic environment and herd size, two variables considered to be related to both the exposure (husbandry practices) and disease (congenital malformations), were used in matching the case-control herds. A total of 32 swine husbandry variables including breeding practices, feeding practices, use of drugs, and water source were evaluated. Only five of the variables were significant ( P = 0.10). This, however, is not considered unusual when 32 variables are tested, even if the null hypothesis is true. Therefore, in the future, environmental studies of swine birth defects may be confined to factors in the natural environment rather than the man-made environment (husbandry).

EPIDEMIOLOGICAL INVESTIGATIONS OF POISONOUS PLANT-INDUCED BIRTH DEFECTS

I. ABSTRACT Epidemiological studies of birth defects induced by poisonous plants have encompassed not only observational studies but also analytical and experimental studies. Epidemiologic investigative techniques have been used as a diagnostic aid to determine what agent, host and environmental factors were associated with a birth defect(s) in domestic animals. Although many of these investigations included laboratory studies, they usually began with field observations on the frequency and pattern of defects in a herd or population that had grazed either in a particular pasture or over a large, defined geographical region. Epidemiologic field studies have suggested that not only the toxic plant but also man-made or other natural environmental factors were associated with defects in domestic animals. The mere presence of the poisonous plant alone was not enough; it must have been consumed. However, field investigations have in many instances been used to determine what poisonous plants probably induced birth defects in domestic animals.

Value and Methods of Animal Studies in Epidemiology

Epidemiological studies of malformations in animal populations have, in general, been limited to domesticated species and may be beneficial from two standpoints. One is the impact that defects have on fetal wastage, especially in food-producing animals where there is a loss of either available animal protein or valuable breeding stock. The second is that of comparative medicine. Such studies can be used to measure and evaluate the impact of teratogenic agents, either defined, suspected, or unknown, upon animal populations. They include evaluation of malformations with similar etiologies, similar clinical manifestations, or involvement of similar anatomical structures. Emphasis has also been placed on the study of defects with similar pathological lesions or those which involve similar organs or body systems (Botts et al., 1966). Thus, the animal frequently is a model for a study of the teratogenic process in man (Doyle et al., 1968; Cornelius, 1969).