An Eight-Year Survey for Canine Distemper Virus Indicates Lack of Exposure in the Endangered Darwin's Fox (Lycalopex fulvipes).

No evidence of exposure to canine distemper virus (CDV) was detected in 70 samples corresponding to 58 wild-trapped Darwin's foxes (Lycalopex fulvipes) in Chile. Given its current endangered status and it being immunologically naïve, in the event of a CDV spillover from dogs to foxes, high population mortality is expected.

SAFETY AND SEROLOGICAL RESPONSE TO MULTIVALENT CANINE DISTEMPER VIRUS VACCINE IN RED FOXES (VULPES VULPES).

Canine distemper virus (CDV) vaccination using commercial vaccines has been recommended as a useful preventive tool in zoological collections worldwide for the past 30 yr. Zoological facilities have not conducted studies to assess the effectiveness and safety of the multivalent Recombitek C6 and C8 in nondomestic carnivores. They are the only CDV recombinant vaccines available in Latin America. Seventeen clinically healthy red foxes born in Buin Zoo were divided into three groups and administered 1 ml of Recombitek C6 vaccine. Group A consisted of three animals of 9 mo of age without previous vaccination (WPV) that received a single dose. Group B consisted of four animals of 10 mo of age WPV; they received a series of three doses with a 21-day interval between doses. Group C consisted of eight animals > 1 yr of age that had received a previous vaccination > 1 yr ago; they received a single-dose booster vaccination. Titers for antibodies against CDV were measured by a serum neutralization test. All animals remained clinically healthy throughout the study period and without clinical signs of disease. Only two foxes (group C) did not show any increase in the antibody titer to the vaccine. All animals of groups A and B seroconverted at 21 days after the first vaccination. Only two animals (both from group B) showed an adequate antibody protective response (titers >100) after 180 days. Absence of adverse reactions in red foxes included in this study supports the safety and apparently nondeleterious effect of CDV recombinant vaccine reported in other nondomestic carnivores. Low antibody response and lack of persistence in the serological response 6 mo after vaccination with a single dose suggested limited protective benefits in this species. Additional research is needed to confirm the antibody titer response to multiple vaccinations in this species.

An rRT-PCR assay to detect the matrix gene of a broad range of avian paramyxovirus serotype-1 strains.

The current U.S. Department of Agriculture (USDA)-validated real-time reverse transcription-polymerase chain reaction (rRT-PCR) assay designed to detect the matrix gene of avian paramyxovirus serotype-1 (APMV-1) is the primary screening assay used in the United States. It has previously been shown to be unable to consistently detect all members of class I APMV-1. Diagnostic testing relies on rRT-PCR to quickly detect APMV-1 in wild birds, backyard flocks, live bird markets, commercial poultry, and for export testing. Limitations of the current USDA assay have raised concerns about the potential for some strains of APMV-1 to remain undetected by the primary screening assay. Mismatches in the probe were shown to cause a loss in template binding efficiency, resulting in lack of detection by the assay. Here, we describe the development and analytical validation of a new rRT-PCR assay designed to target a highly conserved region of the matrix gene across a wide range of APMV-1 strains. Limit of detection testing revealed a 3 log10 decrease in sensitivity for one low-virulence strain when compared to the USDA validated assay. Conversely, the assay showed increased sensitivity for a class I isolate and two virulent strains of APMV-1 that were not detected by the USDA-validated assay. The new assay also demonstrated a high degree of specificity by the lack of detection of 43 non-APMV-1 viruses.

Experimental infection with low and high pathogenicity H7N3 Chilean avian influenza viruses in Chiloe wigeon (Anas sibilatrix) and cinnamon teal (Anas cyanoptera).

Two different wild duck species common in Chile and neighboring countries, Chiloe wigeon (Anas sibilatrix) and cinnamon teal (Anas cyanoptera), were intranasally inoculated with 10(6) mean embryo infective dose (EID50) of the H7N3 low pathogenicity (LP) avian influenza virus (AIV) (A/chicken/Chile/176822/02) or high pathogenicity (HP) AIV (A/chicken/Chile/ 184240-1/02), in order to study the infectivity and pathobiology of these viruses. None of the virus-inoculated ducks had clinical signs or died, but most seroconverted by 14 days postinoculation (DPI), indicating a productive virus infection. Both LPAIV and HPAIV were isolated from oral swabs from two of six Chiloe wigeons and from oral and/or cloacal swabs from all five of the cinnamon teal at 2 DPI. Both LPAIV and HPAIV were efficiently transmitted to cinnamon teal contacts but not to Chiloe wigeon contacts. This study demonstrates that the cinnamon teal and Chiloe wigeons were susceptible to infection with both Chilean H7N3 LPAIV and HPAIV, but only the cinnamon teal showed contact transmission of the virus between birds, suggesting that the cinnamon teal has the potential to be a reservoir for these viruses, especially the LPAIV, as was demonstrated in 2001 with isolation of a genetically related H7N3 LPAIV strain in a cinnamon teal in Bolivia. However, the definitive source of the H7N3 Chilean LPAIV still remains unknown.

Recombination resulting in virulence shift in avian influenza outbreak, Chile.

Influenza A viruses occur worldwide in wild birds and are occasionally associated with outbreaks in commercial chickens and turkeys. However, avian influenza viruses have not been isolated from wild birds or poultry in South America. A recent outbreak in chickens of H7N3 low pathogenic avian influenza (LPAI) occurred in Chile. One month later, after a sudden increase in deaths, H7N3 highly pathogenic avian influenza (HPAI) virus was isolated. Sequence analysis of all eight genes of the LPAI virus and the HPAI viruses showed minor differences between the viruses except at the hemagglutinin (HA) cleavage site. The LPAI virus had a cleavage site similar to other low pathogenic H7 viruses, but the HPAI isolates had a 30-nucleotide insert. The insertion likely occurred by recombination between the HA and nucleoprotein genes of the LPAI virus, resulting in a virulence shift. Sequence comparison of all eight gene segments showed the Chilean viruses were also distinct from all other avian influenza viruses and represent a distinct South American clade.