Doctor of Philosophy (PhD)


Veterinary Medical Sciences - Pathobiological Sciences

Document Type



Among the soil-transmitted helminths (STH), hookworms are a worldwide problem in both humans and animals. They cause non-specific gastrointestinal symptoms, and in young children and animals, they can cause stunting, malnutrition and anemia. Canine hookworms have significant zoonotic potential as a cause of cutaneous larvae migrans and eosinophilic enteritis in humans. To determine the ecological niche of human hookworm in Brazil, two risk models were developed based on the Growing Degree Day-Water Budget (GDD-WB) concept, one based on accumulation of monthly temperatures above a base temperature of 15oC and threshold WB value >0.4. The second was based on a ‘gradient index’ of the product of monthly accumulated GDD and WB values. It was determined that both environmental temperature and moisture are important in the distribution of hookworm. This study supports the validity of the GDD-WB concept for mapping risk of hookworm at a national scale. A cross-sectional survey was conducted in human outpatients in Mutuípe municipality, Brazil, to determine prevalence of soil-transmitted helminths, including hookworm. Mutuípe falls within the permissive zone for the transmission of hookworm. A sucrose double centrifugation flotation technique was used for the concentration of helminth eggs in fecal samples. Hookworm infection was the most prevalent of the STH and the prevalence was highest in adults and males. PCR was then used to determine the species of hookworm present. Necator americanus was confirmed by PCR as the predominant hookworm species. A single case of Ancylostoma ceylanicum was identified. A study on the prevalence of hookworms and other gastrointestinal parasites in shelter dogs in south Louisiana and the anthelminthic protocols used in the shelters was conducted. Fecal samples examined by direct smear, flotation and sedimentation methods revealed that hookworm had the highest prevalence (53.6%) followed by Trichuris vulpis (28.7), Cystoisospora ohioensis (17.2%), Giardia duodenalis (12.0%), C. canis (7.7), Toxocara canis (6.2%), Dipylidium caninum, Alaria spp and Capillaria sp A PCR-RFLP developed to differentiate A. caninum and A. braziliense revealed A. caninum as the only species found. Evaluation of the anthelminthic protocols used in nine shelters showed current methods were inadequate for control of hookworms in shelter dogs.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Malone, John B.