Jerold H. Theis

Acute and chronic complications of laser angioplasty: Vascular wall damage and formation of aneurysms in the atherosclerotic rabbit

Acute and chronic vascular responses to laser exposure in atherosclerotic rabbits were studied. In 7 rabbits fed an atherogenic diet for 3 to 5 months before the study to induce aortic atherosclerosis, a flexible quartz fiber, 400 micron core diameter, attached to an argon ion laser was passed anterogradely or retrogradely to the atherosclerotic ascending aorta. The laser was turned on using power intensities of 1 to 2 W for 3 seconds. After laser treatment, the aortas were studied acutely in 3 rabbits and chronically in 4 rabbits after recovery for 1 to 14 days. In 2 rabbits studied acutely, the argon laser produced a vaporized crater within the atherosclerotic plaque at the endothelial surface; however, in 1 there was also vascular damage extending deep into the medial layer. In addition, aortic aneurysm with muscular wall damage occurred in 2 of the 4 animals studied chronically. Thus, vascular complications may arise when catheter laser angioplasty is randomly applied without visualizing specific plaque targets or without using safe dose increments of power intensities and durations of exposure. This study suggests caution in the clinical use of intensive phototherapy to cardiovascular lesions and stresses the need for further understanding of laser vascular consequences before application of laser angioplasty in patients.

Gray Foxes (Urocyon cinereoargenteus) as a Potential Reservoir of a Bartonella clarridgeiae-Like Bacterium and Domestic Dogs as Part of a Sentinel System for Surveillance of Zoonotic Arthropod-Borne Pathogens in Northern California

ABSTRACT Two species of Bartonella, a novel Bartonella clarridgeiae-like bacterium and B. vinsonii subsp. berkhoffii, were isolated from rural dogs and gray foxes in northern California. A novel B. clarridgeiae-like species was isolated from 3 (1.7%) of 182 dogs and 22 (42%) of 53 gray foxes, while B. vinsonii subsp. berkhoffii was isolated from 1 dog (0.5%) and 5 gray foxes (9.4%). PCR and DNA sequence analyses of the citrate synthase (gltA) gene and the 16S-23S intergenic spacer region suggested that strains infecting dogs and gray foxes were identical. Fifty-four dogs (29%) and 48 gray foxes (89%) had reciprocal titers of antibodies against Bartonella spp. of ≥64. The high prevalence of bacteremia and seroreactivity to Bartonella spp. in gray foxes suggests that they may act as a reservoir species for the B. clarridgeiae-like species in this region. Domestic dogs were also tested for other arthropod-borne infectious agents. Fifty-one dogs (28%) were positive for Dirofilaria immitis antigen, seventy-four (40%) were seroreactive to Anaplasma phagocytophilum, and five (2.7%) were seropositive for Yersinia pestis. Fourteen dogs (7.6%) were PCR positive for A. phagocytophilum. Polytomous logistic regression models were used to assess the association of Bartonella antibody titer categories with potential risk factors and the presence of other vector-borne agents in domestic dogs. Older dogs were more likely to be seroreactive to Bartonella spp. There was no association between the exposure of dogs to Bartonella and the exposure of dogs to A. phagocytophilum in this study.

Seroprevalence of equine piroplasms and host-related factors associated with infection in Greece.

Serum samples were collected from a total of 544 equids that included 524 horses, 13 mules, and 7 ponies from various regions of mainland Greece and were examined by competitive-inhibition ELISA (cELISA) to evaluate the level of exposure of Greek equids to Theileria (Babesia) equi and/or Babesia caballi, the causative agents of piroplasmosis. Association between seropositivity and host-related factors of species, gender, age, origin, activity and location were investigated. The overall seroprevalence was 11.6% (9.1-14.6%) with 95% confidence limit. The seroprevalence for T. equi and B. caballi was found to be 11% (8.6-14%) and 2.2% (1.2-3.9%), respectively. The animal-related factors significantly linked with seropositivity were the species, activities of farming, racing, recreation, and geographic location in Attica, Macedonia, Peloponnese and Thessaly region (p<0.05). The relative risks for the presence of T. equi, B. caballi and mixed infection in mules compared to horses was 8.39, 33.58 and 40.31, respectively. The infection level for T. equi, B. caballi and mixed infection were significantly higher in farm equids than in racing equids (p<0.05). Also, the rate of infection of T. equi was higher in farm equids than recreational equids (p<0.05). The relative risk of T. equi infection between farming equids and equids used only for recreation activity was 3.25-1, while the relative risk of B. caballi infection was 0.14-1 for racing animals relative to recreation animals. The region with the highest level of infection to both parasites was Thessaly (38.8% T. equi and 6.1% B. caballi), followed by Peloponnese (10.4% T. equi and 3.9% B. caballi), Attica region (8.3% T. equi and 0.6% B. caballi) and finally Macedonia the region with the lowest prevalence (6.6% T. equi and 4.4% B. caballi). A higher seroprevalence rate was found among local animals compared to imported equids, indicating that equine piroplasm infection is enzootic in Greece. T. equi seroprevalence was significantly different and higher among increasing age groups of equids, suggesting persistent infections or lower transmission levels whereby animals may need to be exposed longer before acquiring the infection. Competent tick vectors Rhipicephalus bursa and Rhipicephalus sanguineus for the transmission of equine piroplasmosis were recovered from horses and dogs, respectively.

Public health issues concerning the widespread distribution of canine heartworm disease

Heartworms can cause serious cardiopulmonary disease in their canid hosts. Canine heartworm has become widespread in many parts of the world, and its range continues to expand. Wildlife reservoirs play a role in perpetuation and transmission of this parasite to dogs. Human heartworm infection is incidental and is typically not associated with severe clinical disease; however, because no serological test is readily available, patients must undergo invasive procedures to differentiate heartworm from other more serious diseases. Human cases have been reported mainly in areas of high canine prevalence, highlighting the importance of heartworm testing and chemoprophylaxis in all dogs to reduce transmission. Future efforts should focus on the development of a non-invasive diagnostic test for people, and on epidemiological surveys for both animals and people.

Effects of laser irradiation on human thrombus: Demonstration of a linear dissolution-dose relation between clot length and energy density

Because vascular thrombosis often accompanies arteriosclerotic disease in occluding blood vessels, the dissolution properties of laser irradiation were investigated and the energies needed to penetrate different lengths of thrombus were quantitated. Spectrophotometric studies show that the blood clot due to the presence of hemoglobin is well absorbed by argon laser energies, which emit blue-green wavelengths between 454 and 514 nm. Thus, laser energies transmitted directly from an argon-ion source produced vaporization and penetration of human thrombus in a linear dose-response fashion; the longer the thrombus, the greater the power intensity or time exposure necessary to penetrate the clot.

An epidemiologic systems analysis model for African trypanosomiasis

Abstract Systems analysis and simulation modelling were applied to describe the quantitative epidemiology of trypanosomiasis. With the aid of a causal loop diagram, and based on mechanistic decomposition of the components of the trypanosomiasis-tsetse complex, a Forrester flow diagram was developed. Interactions between factors in the system and variables required in the model were estimated from existing data. Appropriate differential equations were set up to describe the dynamics of the model based on mass action theory. Simulation involved integrating birth and death rates, infection and population dynamics as they relate to the carrying capacity of the land, and fluctuations in temperature and rainfall. Both deterministic and stochastic aspects were considered. The model was computerized using a continuous systems modelling program and integration time intervals of one day. Simulations were run using various initial conditions as provided by data from southwestern Ethiopia. The performance of the model was satisfactory when compared with an independent set of data. The procedure enhanced our understanding of the dynamics of the trypanosomiasis-tsetse complex; it could thus be used as a guide to evaluating different programs to control trypanosomiasis in Ethiopia and in other African countries.

Vector Competence of Two Species of Mosquitoes (Diptera: Culicidae) from Southern California for Dirofilaria immitis (Filariidea: Onchocercidae)

Abstract Two species of mosquitoes reared to adults from field-collected larvae or egg rafts in or near Los Angeles County, CA, were exposed to dogs with known levels of Dirofilaria immitis (Leidy) microfilariae per 20 cubic millimeters of blood. Aedes taeniorhynchus (Wiedemann) readily blood fed on an infected dog ingested microfilariae but did not become infected. Culiseta incidens (Thomson) also fed on an infected dog became infected, and 10% of the microfilariae developed to the L3 stage. Cs. incidens is a peridomestic species broadly distributed in Los Angeles County and abundant from February through December. The wide distribution of this species as well as its long annual period of reproductive activity in Los Angeles County may contribute to its potential as a vector of D. immitis.

Autochthonous Human Paragonimiasis in North America

Abstract Imported human paragonimiasis has been reported in the United States. However, autochthonous cases are rare. We describe a case of probable Paragonimus kellicotti infection associated with ingestion of crayfish and review all autochthonous cases in this country.

Evaluation of trypanosomiasis control alternatives using an epidemiologic simulation model

Abstract The effect of various disease-vector control alternatives on the prevalence of trypanosomiasis in southwest Ethiopia was examined with the aid of an epidemiologic model. The alternatives considered included vegetation clearing by manual labor, game elimination, insecticidal spraying from airplanes coupled with settlement, use of sterile male Glossina , avoidance of tsetse infested areas, increasing the resistance of the cattle population, therapy, and combinations of the above methods. First, the currently estimated endemic prevalence of trypanosomiasis (27.3%) in the simulated area of Ethiopia was established and maintained over a 10 year period. Then, various control alternatives were introduced and the simulation was run for an additional 10 years to observe the effect of these control alternatives on the prevalence. The combined use of vegetation clearing, insecticides, therapy, and settlement (or resettlement) was the most effective and feasible method of trypanosomiasis control for the simulated situation.

Epidemic and endemic characteristics of trypanosomiasis in cattle: A simulation model

Abstract A simulation model was utilized to analyze the infection characteristics of trypanosomiasis in Ethiopian cattle. Epidemic and endemic conditions, the threshold phenomenon, proportional distribution of single, multiple and super infections were examined. The results indicate that at the endemic level the prevalence of trypanosomiasis was 0.27 and the incidence varied from 0.007 to 0.01. A large proportion of the infections were of the single type; multiple and surper infections were rare. The importance of such information lies in its usefulness in evaluating control alternatives.