Marco V. Herrero

Field Evaluation of a Multiplex Real-Time Reverse Transcription Polymerase Chain Reaction Assay for Detection of Vesicular Stomatitis Virus

Sporadic outbreaks of vesicular stomatitis (VS) in the United States result in significant economic losses for the U.S. livestock industries because VS is a reportable disease that clinically mimics foot-and-mouth disease. Rapid and accurate differentiation of these 2 diseases is critical because their consequences and control strategies differ radically. The objective of the current study was to field validate a 1-tube multiplexed real-time reverse transcription polymerase chain reaction (real-time RT-PCR) assay for the rapid detection of Vesicular stomatitis New Jersey virus and Vesicular stomatitis Indiana virus strains occurring in Mexico and North and Central America. A comprehensive collection of 622 vesicular lesion samples obtained from cattle, horses, and swine from throughout Mexico and Central America was tested by the real-time RT-PCR assay and virus isolation. Overall, clinical sensitivity and specificity of the real-time RT-PCR were 83% and 99%, respectively. Interestingly, VS virus isolates originating from a specific region of Costa Rica were not detected by real-time RT-PCR. Sequence comparisons of these viruses with the real-time RT-PCR probe and primers showed mismatches in the probe and forward and reverse primer regions. Additional lineage-specific primers and a probe corrected the lack of detection of the missing genetic lineage. Thus, this assay reliably identified existing Mexican and Central American VS viruses and proved readily adaptable as new VS viruses were encountered. An important secondary result of this research was the collection of hundreds of new VS virus isolates that provide a foundation from which many additional studies can arise.

Temporal and spatial variation of phlebotomine (Diptera: Psychodidae) community diversity in a cutaneous leishmaniasis endemic area of Costa Rica.

Abstract Phlebotomine sand fly species composition and diversity were studied in Acosta, an area of Costa Rica endemic for cutaneous leishmaniasis. Two CDC miniature light traps per house were set overnight in 72 houses distributed in 6 localities, once a month, during the rainy seasons of 1994 and 1995. Of the 22 species collected, the most common were Lutzomyia serrana (Damasceno & Arouck), L. youngi Feliciangelli & Murillo, L. ylephiletor (Fairchild & Hertig), L. shannoni (Dyar), L. cruciata (Coquillett), L. gomezi (Nitzulescu), L. sanguinaria (Fairchild & Hertig), and Warileya rotundipennis (Fairchild & Hertig). The Czekanowsky index and the Sorensen index as modified by Bray and Curtis to consider abundance were used to compare species composition and β-diversity. Comparisons were made among localities within years, between years, and localities each year. The data strongly indicated that phlebotomine species composition is more stable than diversity or abundance.

Current status of bluetongue virus in the Americas

The presence of bluetongue virus (BTV) in the Americas is important in part owing to the direct impact of clinical disease on the livestock industry, but more importantly due to the economic impact of restrictions on international trade in animals and animal germplasm. Although, North, Central, and South America are geographically distinct regions and epidemiologically diverse, there is some overlap in terms of the serotypes of BTV and the biting midge vectors that transmit them. Bluetongue has a considerable economic impact in North America, with losses attributed to effects on animal health and productivity as well as nontariff trade restrictions that affect the sale and movement of animals. Currently, there is one nationally licensed vaccine for bluetongue (BT) in the United States for use in sheep only. Homologous killed vaccines are used mostly for captive wildlife breeding farms; however, the primary recommendation for control of BTV in the United States is insect vector control. Recommendations to control the insect vector include removal of potential breeding sites and use of insecticides and repellents.

Survey of Small Rodents and Hematophagous Flies in Three Sentinel Farms in a Costa Rican Vesicular Stomatitis Endemic Region

Abstract: A survey of rodents and hematophagous flies was conducted on three farms located in an area endemic for vesicular stomatitis to determine the species composition of each zoological group occurring in these areas. Eleven species of small rodents were collected and identified. Individuals from forty‐nine species of hematophagous flies of the families Ceratopogonidæ, Culicidæ, and Phlebotominæ were captured and identified. The species compositions in each group were compared between farms. Rodents were tested for antibodies to vesicular stomatitis, New Jersey and Indiana serotypes. Seven species had antibody titers greater than 1:10. Attempts to isolate the virus produced negative results for all the species tested.

Longitudinal studies in the epidemiology of vesicular stomatitis on Costa Rican dairy farms.

Abstract: Twenty‐three Costa Rican dairy herds from an vesicular stomatitis (VS) endemic area were under an active surveillance between April 1997 and March 1999. Ninety‐two confirmed cases of VS New Jersey were found. Factors associated with clinical cases of VS virus New Jersey were: Parity (animals of parity 4 or 5 were 5.3 times more likely to present a clinical case than animals of parity 3 and lower; on the other hand, animals of parity 6 and higher showed an odds 4.6 times greater than animals of parity 3 and lower.) Ecological life zone (animals in premountain moist forest were 7.4 times more likely to present clinical cases than animals in lower mountain rain forest). Factors associated with seropositivity at the time of birth were farm and breed (Jersey calves had an odds 14.7 times greater than Holstein calves). Seroconversion, defined as the first twofold increase in the titers of the blood, was associated with farm and showed four peaks during the study period, September (wet season) 1997, February (dry season) 1998, September 1998, and February 1999. Finally, time to event analysis showed difference between farms and age, older animals showed the first seroconversion earlier than younger animals.