Modeling the distribution and abundance of the non-native parasite, canine heartworm, in California coyotes

We applied a habitat-modeling approach using logistic regression to predict the distribution and abundance of canine heartworm ( Dirofilaria immitis ) in coyotes ( Canis latrans ) throughout California. Heartworm is an arthropod-borne parasite of considerable economic and ecological importance. In California, coyotes serve as the primary sylvatic maintenance host and represent a useful sentinel for this parasite. To develop the model, we used a large collection of coyote blood specimens and carcasses collected from spatially broad, yet nonrandom, locations in California. Survey data were useful in refining previous coarser models that predicted uniformly high prevalence of heartworm throughout the coastal and Sierra-Nevada foothills, by indicating variability within this broadly defined plant-climate zone. Due to the non-random nature and large spatial scale of our data-set, we restricted variables to those thought to be most generally important. Modeling indicated that woodlands with a relatively dense canopy, suitable breeding and host-seeking habitat of the western treehole mosquito ( Ochlerotatus sierrensis ), were a good predictor of heartworm prevalence. Within this habitat, prevalence increased with precipitation, which likely affected mosquito abundance. The distribution of heartworm was limited to areas with average cumulative temperatures high enough to enable larval development of heartworms within their mosquito vectors. The prediction accuracy of our model was supported by goodness-of-fit tests, cross-validation tests and external validation tests. The model provided a useful guide to the relative risk of heartworm exposure in California, although the resolution was necessarily coarse and prevalence estimates related to risk in an ordinal manner only.     

Survey of canine heartworm in the city of Recife, Pernambuco, Brazil.

Six hundred and eleven random-source dogs (338 male, 273 female) one year of age or older, from six sections of the city of Recife, Pernambuco, were examined antemortem for circulating microfilariae Dirofilaria immitis and Dipetalonema reconditum adult heartworm (D. immitis) antigen, and examined postmortem for adult heartworms. The prevalence of heartworm infection was 2.3% (14/611), as determined by necropsy for adult worms, and 1% (6/611) had circulating microfilariae of D. immitis; thus, 57.1% of the heartworm-infected dogs had occult infections. The results of serological testing indicated that 1.3% (8/611) of the dogs were positive for adult heartworm antigen. A total of 42 (6.9%) of the dogs had microfilariae of D. reconditum; 40 of these had only D. reconditum and two additional dogs had microfilariae of both species, D. immitis and D. reconditum.     

Spatial and temporal variation in the seroprevalence of canine heartworm antigen in the island fox

Island foxes (Urocyon littoralis) are endemic to six of the eight California Channel Islands (USA). The island fox is classified as a threatened species by the State of California, and recently three of the six subspecies have experienced abrupt population declines. As part of a continuing effort to determine the cause of the declines, we tested island fox serum samples collected in 1988 (n = 176) and 1997-98 (n = 156) over the entire geographic range of the species for seroprevalence of canine heartworm (Dirofilaria immitis) antigen. Using a commercially available enzyme-linked immunosorbent assay (PetChek, Idexx Laboratories, Westbrook, Maine, USA) we detected heartworm antigen in four of the six populations of island foxes. On San Miguel and Santa Rosa Islands, seroprevalence in adult foxes was >85% (n = 62) in 1988 and increased to 100% (n = 24) in 1997-98. On Santa Cruz Island, seroprevalence in adult foxes decreased from 83% (n = 30) to 58% (n = 26), whereas on San Nicolas Island, seroprevalence increased from 25% (n = 32) to 77% (n = 30) during the same period. All of the pups assayed (n = 33) were seronegative. The seroprevalences of heartworm reported herein for the four populations of island foxes are the highest yet reported for a fox species. However, additional demographic data reported elsewhere suggests that heartworm has not been a major factor in the recent declines of island fox populations.     

Relaxing and contracting activities of heartworm extract on isolated canine abdominal aorta.

Effect of adult heartworm (HW) crude extract on isolated canine abdominal aortic strips precontracted with noradrenaline was examined by recording isometric changes in tension. HW extract caused contraction of the aortic strip at a low concentration (LC) and its relaxation at a high concentration (HC). In aortic strips without endothelium, LC extract elicited a contraction similar to that in the strips with endothelium, whereas HC extract failed to produce any relaxation but instead produced a contraction. The relaxing effect of HC extract was blocked after treatment with 300 microM NG-nitro-L-arginine methyl ester hydrochloride, with reversal by additional treatment with 3 mM L-arginine. It was also markedly reduced or abolished after treatment with 3 microM oxyhemoglobin or 1 microM methylene blue. Fractionation of HW extract by high-performance liquid chromatography revealed that the relaxing and contracting activities are due to different substances in the extract. The results indicate that HW extract contains 2 different vasoactive substances, 1 causing contraction of canine abdominal aorta via a direct action on the smooth muscle, and the other its relaxation indirectly by releasing nitric oxide from endothelial cells. These vasoactive substances might play a role in HW extract-induced shock in dogs, and in the pathogenesis of HW infection.     

Ethical issues concerning animal research outside the laboratory

Unique ethical issues can be associated with research outside the customary laboratory setting. Protocols involving wild animals must consider that any infringement on the wild nature of the species can be disruptive and may involve pain, fear, anxiety, and frustration, all of which constitute ethical harm that must be balanced with anticipated benefit. Agricultural and companion animal research, however, take place in a human-engineered environment and involves domesticated species adapted to human contact. Special animal welfare issues can be related to agricultural production goals that fail to deal adequately with moral concerns. Human/companion animal relationships, on the other hand, present unique moral obligations to animal owners. Other factors may present additional ethical issues when research is performed outside the laboratory. These factors include a required sensitivity to the environment of wild animals and an awareness that this outside research may to quite public and, therefore, vulnerable to community perception. The institutional animal care and use committee(IACUC) has the responsibility to ensure that research in outside settings is ethical and properly implemented. This responsibility requires that IACUC members have knowledge of the needs of a wide range of species and that a process is in place to allow effective monitoring of research in remote locations. Finally, and most important, there must be a sensitivity to the unique ethical considerations outlined here. Armed with these strengths, the IACUC will be effective in what may be unfamiliar surroundings and will have a significant opportunity to cause improvements in animal welfare.     

Public health surveillance and infectious disease detection

Emerging infectious diseases, such as HIV/AIDS, SARS, and pandemic influenza, and the anthrax attacks of 2001, have demonstrated that we remain vulnerable to health threats caused by infectious diseases. The importance of strengthening global public health surveillance to provide early warning has been the primary recommendation of expert groups for at least the past 2 decades. However, despite improvements in the past decade, public health surveillance capabilities remain limited and fragmented, with uneven global coverage. Recent initiatives provide hope of addressing this issue, and new technological and conceptual advances could, for the first time, place capability for global surveillance within reach. Such advances include the revised International Health Regulations (IHR 2005) and the use of new data sources and methods to improve global coverage, sensitivity, and timeliness, which show promise for providing capabilities to extend and complement the existing infrastructure. One example is syndromic surveillance, using nontraditional and often automated data sources. Over the past 20 years, other initiatives, including ProMED-mail, GPHIN, and HealthMap, have demonstrated new mechanisms for acquiring surveillance data. In 2009 the U.S. Agency for International Development (USAID) began the Emerging Pandemic Threats (EPT) program, which includes the PREDICT project, to build global capacity for surveillance of novel infections that have pandemic potential (originating in wildlife and at the animal-human interface) and to develop a framework for risk assessment. Improved understanding of factors driving infectious disease emergence and new technological capabilities in modeling, diagnostics and pathogen identification, and communications, such as using the increasing global coverage of cellphones for public health surveillance, can further enhance global surveillance.     

Public health: the control of meningococcal disease in Quebec

A first outbreak of serogroup C meningococcal disease occurred in the province of Quebec in 1990-1992 and lead to a mass immunization campaign using polysaccharide vaccines. In 2001, a second outbreak was identified and a mass vaccination campaign was carried out, using the newly licensed conjugate vaccine. Clinical, epidemiological, economic and social studies were instrumental in the decision making for implementing these control programs.     

The widespread occurrence and tissue distribution of the imidazolopyrazine luciferins

Bioluminescence has been reported to occur in 17 phyla and at least 700 genera. However, the luciferin chemistry of the majority of luminous organisms has yet to be determined. The most common chemistry which is known to occur in deep sea bioluminescence is imidazolopyrazine bioluminescence. The main aim of this study was to examine the phyletic and tissue distribution of imidazolopyrazine luciferins. This will facilitate analysis of imidazolopyrazine bioluminescence at the cellular and molecular levels and, in particular, how and when its chemistry is controlled and expressed in vivo. Assays for both known imidazolopyrazines were established and a range of fresh organisms and tissue were analysed, i.e. fish, cephalopods, copepods, ostracods, amphipods and euphausiids. The main findings were that the number of genera in which coelenterazine has been detected has been increased from 52 to about 90. Also, for the first time, the other known imidazolopyrazine luciferin,Vargula-type luciferin, was quantified in the ostracod Cypridina dentata, but was not detected in any of its potential predators. Neither imidazolopyrazine luciferin was found in several luminous stomiiform fish assayed. Coelenterazine was measured in the livers and photophores of a number of cephalopods and it is apparent that coelenterazine is responsible for both modes of luminescence. © 1997 John Wiley & Sons, Ltd.     

Inference of population structure and patterns of gene flow in canine heartworm (Dirofilaria immitis)

Understanding the genetic variation within a parasitic species is crucial to implementing successful control programs and preventing the dispersal of drug resistance alleles. We examined the population genetics and structure of canine heartworm (Dirofilaria immitis) by developing a panel of 11 polymorphic microsatellite loci for this abundant parasite. In total, 192 individual nematodes were opportunistically sampled from 9 geographic regions in the United States and Mexico and genotyped. Population genetic analyses indicate the presence of 4 genetic clusters. The canine heartworm samples used in this study were characterized by low heterozygosity, with eastern and central North America experiencing high levels of reciprocal gene flow. Geographic barriers impede the movement of vectors and infected hosts west of the Rocky Mountains and south of the Central Mexican Plateau. This, combined with corridors of contiguous habitat, could influence the spread of drug resistance alleles.     

Public information for the assessment of quality: a widespread social phenomenon

We propose that the use of public information about the quality of environmental resources, obtained by monitoring the sampling behaviour of others, may be a widespread social phenomenon allowing individuals to make faster, more accurate assessments of their environment. To demonstrate this (i) we define public information and distinguish it from other kinds of social information; (ii) we review empirical work demonstrating the benefits and costs of using public information to estimate food patch quality; (iii) we examine recent work showing that individuals may also be using public information to improve their estimates of the quality of such disparate environmental parameters as breeding patches, opponents and mates; and finally (iv) we suggest avenues of future work to better understand the nature of public information use and when it might be used or ignored. Such work should lead to a more complete understanding of the behaviour of individuals in social aggregations.     

Public health strategies for distribution of influenza vaccine during an influenza pandemic

In order to consider the ethical issues around vaccine distribution during an influenza pandemic, it is critical to have an understanding of the role of influenza vaccine in a pandemic, the rate at which vaccine is likely to be come available, who will likely produce and "own" the vaccine, how vaccine distribution and administration might be accomplished, and which are the groups that might be deemed highest priority to be vaccinated against influenza. The United States and Connecticut have been considering the more challenging of these issues and have learned from Canada, which previously discussed and made decisions on the challenges related to vaccine distribution. Although there is still some critical advance thinking that needs to be done, planning for the response to an influenza pandemic is now at an advanced stage. The keys to preparedness at this stage are to be aware of the vaccine distribution options, to know the benefits and limitations of each option, and to be flexible but nimble in dealing with a real pandemic.     

Regulatory issues concerning the safety, efficacy and quality of herbal remedies

Herbal remedies and alternative medicines are used throughout the world, and in the past herbs were often the original sources of most drugs. Today we are witnessing an increase in herbal remedy use throughout the Western world raising the question as to how safe are these preparations for the unborn fetus? Many women use herbal products during pregnancy. The dilemma facing most regulatory authorities is that the public considers these products as either traditional medicines or natural food supplements. The user sees no reason for regulation. Most countries have laws concerning foods, drugs, and cosmetics, the details of which seldom clearly define to what section of the law and regulations alternative remedies belong. In most countries alternative remedies are regulated as foods, provided that no medicinal claim is made on the label. The global regulatory sector, however, is changing rapidly. The Therapeutic Goods Administration (TGA) in Australia created a Complimentary Medicines Evaluation Committee in late 1997 to address this issue, and Canada has created a new Natural Health Products Directorate in the realigned Therapeutic Products and Foods Branch in 2000. In parallel, the European Agency for the Evaluation of Medicinal Products has drafted test procedures and acceptance criteria for herbal drug preparations and herbal medicinal products. In the US, the Food and Drug Administration classifies these natural products as dietary supplements. Manufacturers must label a dietary supplement thus: “this statement has not been evaluated by the FDA [, and] this product is not intended to diagnose, treat, cure or prevent any disease.” Whether these products are foods or drugs is undecided. To add complexity to this issue, most of the potential deleterious effects of natural products on the unborn may be related to hormonal effects (e.g., phytoestrogens) and nutriceutical drug interactions (e.g., St. John's Wort and antidepressants), rather than direct embryotoxicity per se. We suggest that ensuring quality of herbal products should receive immediate attention by regulatory authorities, before embarking on the more arduous tasks of safety and efficacy. Birth Defects Res B 68:505–510, 2003. © 2003 Wiley‐Liss, Inc.