Strategies of the control of an outbreak of leptospiral infection in dairy cattle in Northeastern Brazil

Is microscopic agglutination test a reliable method for diagnosing the bovine genital leptospirosis syndrome?

Bovine Genital Leptospirosis (BGL) is a chronic reproductive syndrome characterized by genital infection by Leptospira spp. An accurate diagnosis of BGL is crucial to implementing proper control measures in field conditions. This study aimed to evaluate the reliability of serology by Microscopic Agglutination Test (MAT) for diagnosing leptospirosis in subfertile cows with genital infection. Of three herds, 93 non-pregnant cows with reproductive failures were submitted to the blood sampling (serology by MAT) and genital samples (lipL32-PCR). A total of 62/93 (66.6%) cows presented seroreactive to cutoff 100, while 45/93 (48.4%) cows were positive to cutoff 200, mainly against the Sejroe serogroup. In PCR analysis, 55/93 (59.1%) were positive. MAT results were compared with PCR (considered the standard), and test parameters and Cohen's kappa (ƙ) were calculated for the cut-offs 100 and 200. A ROC curve was performed for each cut-off of titers 100 to 1,600. The sensitivity and specificity of MAT100 were calculated at 66.6% and 33.3%, while for MAT200 the sensitivity was estimated as 35% and specificity as 54.5%. The accuracy of MAT was poor, being 54.8% in MAT100 and 42% in MAT200. Furthermore, the area under the curve of ROC analysis was low for all titers, and the correlation was poor for MAT100 and MAT200 (ƙ < 0). The results demonstrated that MAT is a limited technique to diagnose bovine genital carriers individually, and if only MAT is applied, genital carriers may pass undetected, impairing the control programs.

Molecular epidemiology of Leptospira spp. serogroup Sejroe associated with chronic bovine leptospirosis

Pathogenic bacteria Leptospira spp. are commonly associated with bovine leptospirosis, characterized chiefly by chronic and subclinical reproductive disorders. Strains from the Sejroe serogroup play a significant role in these chronic genital infections known as Bovine Genital Leptospirosis (BGL), which notably impact cattle health. This study aims to deepen our understanding of BGL by investigating the genetic diversity, geographical distribution, and specific anatomical sites of infection of the causative agents. Initially, uterine fragments and cervicovaginal mucus were collected from 47 cows and subjected to PCR targeting the lipL32 gene. Positive samples in lipL32-PCR (9 samples) underwent genotyping based on the secY gene. Subsequently, sequences were aligned with GenBank entries (108 sequences) and analyzed in silico. All nine sequences from this study were identified as L. interrogans with an identity >99 % to serogroup Sejroe reference strains (Norma and L53). In the broader analysis, the most prevalent species observed was L. borgpetersenii, followed by L. interrogans and L. santarosai. The haplotype network of L. interrogans revealed that haplogroups B and C exclusively included L. interrogans strains of genital origin, while haplogroup A encompassed strains from renal sources as well. These findings underscore the significance of the L. borgpetersenii genotype Hardjobovis and L. interrogans genotype Hardjoprajitno as the predominant circulating strains and highlight the existence of distinct haplogroups of pathogenic leptospires originating from genital sources. We advocate for the use of secY as an effective genetic marker for Leptospira spp. and stress the necessity for additional research prioritizing the genital tract. The outcomes of this study contribute to the development of improved control measures for chronic cattle diseases and provide valuable guidance for future investigations.

Bovine Genital Leptospirosis: An Update of This Important Reproductive Disease

Bovine leptospirosis is an important disease that affects the reproductive sphere. Due to its high relevance for the bovine production chain in a worldwide scenario, a better understanding of the disease is crucial to reduce its negative impacts. The main agents are strains from the Sejroe serogroup, such as Hardjo and Guaricura, which lead to renal and genital infection. The genital colonization causes a chronic, silent, and subclinical reproductive syndrome, called Bovine Genital Leptospirosis (BGL). Embryonic death, estrus repetition, subfertility, and abortions are the main signs of BGL condition in females. However, although leptospires have been identified in semen, the manifestation of BGL in bulls remains to be clarified. The recommended diagnosis of BGL includes a serologic screening of the herds using the microscopic agglutination test followed by PCR of genital samples (cervicovaginal mucus, uterine fragment, or semen), especially from animals with reproductive failures. After the identification of carriers, control is carried out considering three steps: antimicrobial treatment of the carriers, environmental and reproductive management, and herd vaccination. Systematic testing, quarantine of newly arrived animals, and usage of antimicrobials in semen diluents or embryo culture media are other sanitary approaches that are encouraged to improve the control of the syndrome. Herein we discuss protocols for an efficient diagnosis and preventive procedures of BGL, which are fundamental to reducing the negative impact of the disease on cattle reproduction and its consequent economic hazards.

Bovine Leptospirosis in Caatinga Biome, Brazil: New Insights into Diagnosis and Epidemiology

Bovine leptospirosis causes economic losses and raises public health concerns. It is possible that there are peculiarities in the epidemiology of leptospirosis in regions with a semiarid climate, such as the Caatinga biome in Brazil, where the climate is hot and dry, and the etiological agent require alternative routes of transmission. This study aimed to close knowledge gaps to the diagnosis and epidemiology of Leptospira spp. infection in cows from the Caatinga biome, Brazil. Samples of the blood, urinary tract (urine, bladder and kidney) and reproductive tract (vaginal fluid, uterus, uterine tube, ovary and placenta) were collected from 42 slaughtered cows. Diagnostic tests included were the microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Anti-Leptospira spp. antibodies were found in 27 (64.3%) of the animals analyzed using MAT at a 1:50 dilution (cut-off 50), while 31 (73.8%) animals had at least one organ/fluid where the presence of Leptospira spp. DNA was identified, and 29 animals (69%) were positive at bacteriological culture. The highest sensitivity values for MAT were obtained at the cut-off point of 50. In conclusion, even under hot and dry climate conditions, it is possible that Leptospira spp. can spread through alternative routes such as venereal transmission; moreover, a cut-off of 50 is recommended for the serological diagnosis of cattle from the Caatinga biome.

New insights on Leptospira sp. infection in ewes maintained in field semiarid conditions

Leptospirosis is poorly studied in small ruminants raised in field semiarid conditions. In this study we compared serological, bacteriological and molecular diagnostic methods in ewes maintained in field Brazilian semiarid conditions. Blood, vaginal fluid and urine samples were collected from 60 Morada Nova ewes raised in a semi-intensive system in the Brazilian semiarid. Diagnostic tests performed were microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Anti-Leptospira sp. antibodies were found in eight (13.33%) animals analyzed by MAT at reciprocal titer 25 (cut-off 25), while Leptospira sp. DNA was detected in urine or vaginal fluid of 56 animals (93.33%). There was growth of leptospires in 10 urine cultures and in 11 vaginal fluid cultures, however, two of urine (2/60-3.33%) and eight cultures of vaginal fluid (8/60-13.33%) were confirmed by PCR. Two samples of vaginal fluid (one of each animal) were submitted to sequencing demonstrating 99% similarity with L. santarosai and L. interrogans. The highest MAT sensitivities were obtained with reciprocal titer 25 (cut-off 25) compared to 50 and 100. The performance of different diagnostic techniques for leptospirosis in ewes raised in field semiarid conditions allowed a better evaluation of the herd, as well as made it possible to identify carrier animals. Genital route may be important for efficient transmission and without dependence on environmental factors in ewes from semiarid, as well as it's highlighted that titer 1:25 in serology was more efficient, indicating its use in ewes in field semiarid conditions.

Bovine Genital Leptospirosis and reproductive disorders of live subfertile cows under field conditions

Bovine genital leptospirosis (BGL) is characterized by silent chronic reproductive disorders, most related to early embryonic death leading to estrus repetition, subfertility and abortions. However, most studies were conducted in slaughterhouses, which lacks reproductive and sanitary history of the studied animals. This study aimed to evaluate the occurrence of Leptospira sp. infection in live cows with history of low reproductive efficiency. Blood, urine, cervico-vaginal mucus and uterine fragment were collected from nine cows of the same herd presenting reproductive failure (abortions, estrus repetition and chronic infertility). Serology (MAT) and molecular analysis (PCR and nucleotide sequencing) were performed. Serology showed three (33.3%) seroreactive cows, two to Sejroe and one to Icterohaemorrhagiae serogroups. Six cows (66.7%) presented leptospiral DNA on genital samples, while all urine samples were negative. L. interrogans was identified in five samples, very closely related to strains from Sejroe (n = 3) and Icterohaemorrhagiae (n = 2) serogroups, while L. noguchii was identified in one sample. Results from this preliminary study demonstrates the presence of leptospires on uterus and reinforces the negative impact of leptospiral infection on reproductive tract, highlighting its association with reproductive failures on live animals.

An overview on the molecular diagnosis of animal leptospirosis

The most common presentation of animal leptospirosis is the subclinical and silent chronic form, that can lead to important reproductive disorders. The diagnosis of this chronic form remains a challenge. The aim of the present study is to gather and critically analyse the current information about molecular tools applied to animal leptospirosis diagnosis, particularly the silent chronic presentation of the infection. Regarding clinical specimens, samples from urinary tract were the most used (69/102, 67·7%), while few studies (12/102, 11·8%) investigated samples from reproductive tract. Concerning the molecular methods applied, the most used is still the conventional polymerase chain reaction (PCR) (46/102, 45%), followed by real-time PCR (38/102, 37·2%). The lipL32 gene is currently the most common target used for Leptospira detection, with 48% of studies applying this genetic marker. From all the studies, only few (21/102, 20·5%) performed gene sequencing. According to the majority of authors, current evidence suggests that lipL32-PCR is useful for an initial screening for Leptospira DNA detection in animal clinical samples. Posteriorly, if DNA sequencing could be performed on positive lipL32-PCR samples, we encourage the use of secY gene as a genetic marker. The molecular methods appear as the most important tools for the diagnosis of the chronic silent leptospirosis on domestic animals, reinforcing its evident impact not only on animal reproduction but also on a One Health context.

Spatial distribution of leptospirosis incidence in the Upper Yangtze and Pearl River Basin, China: Tools to support intervention and elimination

BACKGROUND

Since 2011 human leptospirosis incidence in China has remained steadily low with persistent pockets of notifications reported in communities within the Upper Yangtze River Basin (UYRB) and Pearl River Basin (PRB). To help guide health authorities within these residual areas to identify communities where interventions should be targeted, this study quantified the local effect of socioeconomic and environmental factors on the spatial distribution of leptospirosis incidence and developed predictive maps of leptospirosis incidence for UYRB and PRB.

METHODS

Data on all human leptospirosis cases reported during 2005-2016 across the UYRB and PRB regions were geolocated at the county-level and included in the analysis. Bayesian conditional autoregressive (CAR) models with zero-inflated Poisson link for leptospirosis incidence were developed after adjustment of environmental and socioeconomic factors such as precipitation, normalized difference vegetation index (NDVI), modified normalized difference water index (MNDWI), land surface temperature (LST), elevation, slope, land cover, crop production, livestock density, gross domestic product and population density.

RESULTS

The relationship of environmental and socioeconomic variables with human leptospirosis incidence varied between both regions. While across UYRB incidence of human leptospirosis was associated with MNDWI and elevation, in PRB human leptospirosis incidence was significantly associated with NDVI, livestock density and land cover. Precipitation was significantly and positively associated with the spatial variation of incidence of leptospirosis in both regions. After accounting for the effect of environmental and socioeconomic factors, the predicted distribution of residual high-incidence county is potentially more widespread both in the UYRB and PRB compared to the observed distribution. In the UYRB, the highest predicted incidence was found along the border of Chongqing and Guizhou towards Sichuan basin and northwest Yunnan. The highest predicted incidence was also identified in counties in the central and lower reaches of the PRB.

CONCLUSIONS

This study demonstrated significant geographical heterogeneity in leptospirosis incidence within UYRB and PRB, providing an evidence base for prioritising targeted interventions in counties identified with the highest predicted incidence. Furthermore, environmental drivers of leptospirosis incidence were highly specific to each of the regions, emphasizing the importance of localized control measures. The findings also suggested the need to expand interventional coverage and to support surveillance and diagnostic capacity on the predicted high-risk areas.

Genital bovine leptospirosis: A new look for an old disease

Bovine leptospirosis is often associated with host-adapted leptospires infections, such as strains belonging to the Sejroe serogroup. Although bovine leptospirosis by adapted strains may result in abortions, fetal death, premature births and the birth of weak and/or low-weight calves, this infection is more closely associated with subtler syndromes, such as subfertility and early embryonic death. In this way, this silent disease can go unnoticed and undiagnosed, compromising reproductive efficiency with a consequent decrease in the productivity of herds over long periods. For many years, genital tract infection has been considered a secondary effect of renal infection with the assumption being that leptospires are found in the genital tract due to bacteremia caused by renal colonization. In contrast to this hypothesis, there is some evidence in the literature that suggests that genital leptospirosis should be considered a specific syndrome dissociated from renal/systemic disease. Therefore, this paper aims to gather and critically analyze information about genital leptospirosis in cattle, considering the disease a distinct syndrome, herein denominated bovine genital leptospirosis (BGL), that requires a unique approach to diagnosis and treatment.