Potential Transmission of Bacteria, Including Streptococcus equi spp., Between Stables via Visitors' Clothes

Prevalence and antimicrobial susceptibility of Streptococcus equi isolated from horses in Santa Catarina state, Southern Brazil

The objective of this study was to determine the prevalence of Streptococcus equi (S. equi subsp equi and S. equi subsp zooepidemicus) in the state of Santa Catarina and evaluate the antimicrobial susceptibility of the isolates. For this, 420 nasal swab samples were collected from randomly selected horses. Isolation and phenotypic characterization of the bacteria were performed by sowing on 5% sheep blood agar, followed by analysis of morphotinctorial characteristics and biochemical analysis. To differentiate the main beta-hemolytic Streptococcus in horses, the fermentation profiles of the sugar's lactose, maltose, sorbitol, and trehalose were used, which were confirmed at the subspecies level by the PCR technique. The antimicrobial susceptibility panel was defined by the disk diffusion method, testing 13 antimicrobials from ten different classes, all regularly used in equine medical clinics, followed by the calculation of the multiple antimicrobial resistance index. Ten strains of S. equi were isolated, with a prevalence of 2.38% (10/420). Of the total positive samples, 3% (3/10) were confirmed as belonging to S. equi subsp equi and 70% (7/10) were confirmed as belonging to S. zooepidemicus. Multidrug resistance was observed in 60% (6/10) of isolates. The antimicrobial with the greatest resistance was clindamycin with 70% (7/10), followed by beta-lactams, with 40% (4/10) resistance to penicillin and 30% (3/10) to ceftiofur. The isolates were 100% (10/10) sensitive to gentamicin, chloramphenicol, levofloxacin, and vancomycin. This was the first study carried out in the state, and based on these data, it can be said that Santa Catarina has a low prevalence of S. equi and the presence of multi-resistant strains of S. equi was confirmed in the equine herd in Santa Catarina.

Factors Influencing Equine Affiliate Opinion on Reporting of Equine Strangles in the United States

Although equine strangles is reportable in all states, synchronous reporting of this disease does not occur across the country. States have variable regulations on reporting (actionable, notifiable, and monitored) and no mandatory comprehensive databases exist for tracking prevalence. In this study, which is a companion to our recent publication on veterinarians' opinions on this topic, we solicited equine affiliates' (including horse owners, horse business owners/trainers, breeders, and barn managers) opinions on reporting of strangles and factors influencing their opinion. A total of 518 equine affiliates/stakeholders living within the United States. A structured survey was administered online. Eighty-one participants (17.8%) believed that strangles should continue to be nationally monitored and that individual states should have jurisdiction over laboratory confirmed positive cases; 124 (27.2%) believed strangles should become nationally monitored with mandatory notification of positive cases to a central forum; 77 participants (16.9%) thought strangles should become notifiable nationally; and 157 (34.4%) thought strangles should become notifiable and actionable. Participants who ranked strangles as "important" or "very important" compared to other infectious disease were more likely to want increased reporting (OR = 3.62, P = .054), and participants who were more familiar with the disease were more likely to rank it as important: for every 1-point increase in correct total score on the 5-question basic knowledge exam included, there was a 49% increase in odds of ranking strangles as important or very important (P = .003). Equine stakeholders who perceived their horses to be at medium or high risk of acquiring the disease were 2.76 times more likely to rank strangles as important or very important (P = .014). Of the sampled equine stakeholder community, the majority of respondents (78.5%) favored increased reporting. Information obtained in this study regarding current views of those involved in the equine industry on strangles reporting could inform future policy regarding the disease.

Effectiveness of Cleaning and Sanitation of Stable Environment and Riding Equipment Following Contamination With Streptococcus equi Subsp. equi

Streptococcus equi subsp. equi (S. equi) is transmitted via contact with infected horses or fomites such as equipment or surfaces of the stable environment. Effective cleaning and sanitation is essential to minimize risk of fomite-associated infections. This study assessed the effectiveness of cleaning and sanitation of experimentally S. equi contaminated materials and equipment found in stables. Wood, concrete, plastic, leather halters, leather gloves and polyester webbing halters were inoculated with a 24-hour culture S. equi laboratory strain. In addition, selected materials were inoculated with a clinical strain of S. equi. Three days post inoculation all materials were sampled for retention of viable S. equi and a subset of each material was cleaned and sanitized. After an additional 2 days all treated and untreated materials were sampled for continued retention of viable S. equi. Separate subsets of contaminated polyester halter material were washed at 40^°C with or without drying at 70^°C, or washed at 60^°C. After cleaning and sanitation, all samples except polyester halters were culture negative. Even before cleaning and sanitation leather appears to poorly support survival of S. equi. After washing at 40^°C and tumble drying, 14 of 16 halters were culture positive, however culture negative when washed at 60^°C. Routine cleaning and sanitation of fomites contaminated with S. equi was generally effective to eliminate viable bacteria. However, survival between materials and strains differed, with leather poorly permissive to S. equi survival even without cleaning, whereas polyester webbing halters retained viable S. equi even after washing at temperatures of 40^°C.

Repeated nasopharyngeal lavage predicts freedom from silent carriage of Streptococcus equi after a strangles outbreak

Background

The value of repeated nasopharyngeal lavage (NPL) to detect silent carriers of Streptococcus equi has not been investigated.

Hypothesis/Objectives

Determine if results of serial testing for S. equi by NPL predicts subsequent true carrier status as determined by both NPL and guttural pouch lavage.

Animals

An outbreak of strangles with 100% morbidity in 41 mature Icelandic horses was followed prospectively to investigate development of silent carriers. All were initially positive to S. equi on NPL. The farm was closed to horse movement during the entire study.

Methods

Prospective observational study. Testing for S. equi was performed by NPL at weeks 18, 28, 29, and 30 postindex case and subsequently at week 45 by both NPL and guttural pouch lavage. Carrier status at week 45 was compared to results obtained at weeks 18, 28, 29, and 30. Descriptive statistics were calculated. Comparisons were made using Fisher's exact test or the Freeman‐Halton extension with a P < .05 level of significance.

Results

Of 24 noncarriers at week 45, only 4 horses were negative on all 3 consecutive weekly NPL samples at weeks 28 to 30. However, 10 of the 11 horses with at least 3 negative NPL obtained from weeks 18, 28, 29, and 30 were S. equi‐free at week 45 (P = .03).

Conclusions and Clinical Importance

Repeated NPL on at least 3 separate occasions can assist in predicting S. equi carrier‐free status in horses after recovery from a strangles outbreak.

Potential for residual contamination by Streptococcus equi subspp equi of endoscopes and twitches used in diagnosis of carriers of strangles

BACKGROUND

Endoscopic examinations are essential for diagnosis and treatment of strangles (S equi infection) in horses. However, even after disinfection, endoscopes may retain viable bacteria or bacterial DNA. Twitches are commonly used during endoscopic examinations and can thus also potentially transmit the organism to other horses.

OBJECTIVES

To evaluate the efficacy of different disinfectant methods to eliminate S equi from experimentally contaminated endoscopes and twitches and the effectiveness of field disinfection of endoscopes used in sampling carriers of S equi.

STUDY DESIGN

Experimental contamination and observational field study.

METHODS

One endoscope and 30 twitches were contaminated with standardised S equi broth solutions. The endoscope was disinfected following three protocols using various disinfectants for manual disinfection. A fourth protocol used an automated endoscope reprocessor (AER). The twitches (n = 30) were disinfected following eight different disinfecting protocols. Three endoscopes used in sampling for silent carriers were disinfected following a field-based protocol. After each protocol the endoscopes and twitches were sampled for S equi by culture and qPCR.

RESULTS

Following experimental contamination all endoscope disinfection protocols, apart from 1/6 of the ethanol protocol were S equi culture negative. However, no endoscope disinfection protocol completely eliminated retention of S equi DNA. Field disinfection of endoscopes after sampling carriers yielded no culture positives and all but one (13/14) were qPCR negative. All twitches disinfected following experimental contamination were culture negative but sodium hypochlorite was the only disinfectant that completely eliminated detection of S equi DNA.

MAIN LIMITATIONS

Experimental contamination may not reflect the numbers of S equi transferred to endoscopes or twitches during use on silent carriers and purulent secretions from infected horses may influence survival of S equi.

CONCLUSIONS

While most disinfection methods appear to ensure removal of cultivable S equi, residual DNA can remain on both endoscopes and twitches.