Int. J. Life. Sci. Scienti. Res., 4(5): 2012-2018, September 2018

 

Histopathologically and RT-PCR Detection of the Etiology of Paratuberculosis in Tissues of Clinical Suspected Small Ruminants

 

Mohamed Alamin Ibrahim Hamid¹*, Galal Eldin Elazhari Mohammed², Amel Omer Bakhiet³, Elhassan Mohamed Ali Saeed⁴

 

¹Lecturer, Department of Microbiology, Faculty of Vet. Sci. West Kodrofan University, Alnihood, Sudan

²Professor, Department of Microbiology Pathology and Parasitology, Faculty of Vet. Med., Sudan University of Science and Technology, Khartoum, Sudan

³Professor, Deanship of Scientific Research, Sudan University of Science and Technology, Khartoum, Sudan

⁴Associate Professor, Department of Vet.  Med., College of Agriculture and Veterinary Medicine, Qassim University, Buraydah, Saudi Arabia

 

^*Address for Correspondence: Mr. Mohamed Alamin Ibrahim Hamid, M.Sc., Lecturer, Dept. of Bacteriology, Faculty of Veterinary Science, West Kordofan University, Sudan

 

ABSTRACT- Paratuberculosis remains one of the most obstacles limit animal breeding sector all over the world. The current study aimed to detect the etiology of paratuberculosis in tissues of clinically suspected small ruminants using histopathological and real-time polymerase chain reaction (RT-PCR) methods. Clinical examination showed 10 (26.4%) PTB suspected cases out of the total examined (38) animals. The suspected cases were euthanized, necropsied, gross lesions were recorded and tissues samples were collected for histopathological and molecular procedures. Grossly intestinal and mesenteric lymph nodes thickening, corrugation and edematous swelling were recorded.  Semi-thin sections of the intestine and mesenteric lymph nodes stained with toluidine blue demonstrated MAP organism inside epithelium cells and macrophages. RT-PCR detected MAP IS900 gene in all suspected cases (100%) so we recommend using RT-PCR as a rapid sensitive method in the diagnosis of PTB.

KEYWORDS:  Paratuberculosis, Mycobacterium, Semi thin sections, Toluidine blue, IS900 gene 

 

INTRODUCTION- Paratuberculosis (PTB) is a chronic debilitating incurable granulomatous disease affects cattle, sheep, goats, deer, camelids and wild ruminants worldwide. The disease has also reported in other animals like wild rabbits, pigs, horses, birds and carnivores ^[1-3]. PTB leads to severe economic losses due to productivity reduction, deaths and cost of control programs. The disease is caused by Mycobacterium avium subsp. paratuberculosis (MAP) the causative agents of Crohn's disease of a man so the disease ranked as one of zoonoses and classed in risk group -2 for human infection ^[4,5]. The disease has unusual long-term incubation period with developing of proliferative granulomatous/ lepromatous enteritis which results in subclinical digestive symptoms later may progress to severe clinical signs according to the affected host. Clinical JD is observed mostly in adult animals with characteristic signs including intermitted or progressive projectile watery diarrhea leading to emaciation, wasting and loss of production. Pathological lesions related to the chronic enteritis are found at necropsy ^[6,7]. Over a period in the infected host, MAP organisms proliferate extensively in tissues of an infected host which could be easily demonstrable in tissues and faeces by genetic tests. Regular screening of the farm animals by a number of tests including bacterial culture, ELISA, PCR and necropsy of the dead animals provide evidence of MAP infection. At necropsy and histopathology, ruminant showing granulomatous enteritis with demonstrable an abundant Acid Fast Bacteria are tentatively diagnosed as cases of paratuberculosis ^[8]. Molecular tests since the discovery of IS900 gene ^[9], offer a great promising, sensitive and specific diagnostic assays for detection of MAP infection. Real-time PCR assays are endowed with higher sensitivity and help in determining the load of infection in environmental samples, faeces, and milk ^[10]. The application of PCR to detect genome directly from tissues is a practical and valuable approach for laboratory confirmation of infectious diseases. Therefore this study aimed to an application of real-time polymerase chain reaction and histopathology section in tissues samples of small ruminants in the investigated area.

 

MATERIAL AND METHODS

Clinical examination and sampling- A total number of 38 small ruminants were examined for suspicion of PTB infection in AL Qassim region. The selection based on history and clinical examination. The animals showed signs of emaciation, not curable diarrhea or softened feces, pasty stool and chronic history of weight loss were suspected to be PTB infected (n=10) 5 sheep and 5 goats. The suspected cases were euthanized and examined for gross pathology. The intestine tissues and mesenteric lymph nodes were taken and prepared for histopathological examination and extraction of DNA for RT-PCR method. The study proceeds from February - October 2015 in Department of Clinical laboratory, Teaching Hospital, AL Qassim region, Saudi Arabia.

Histopathologically procedure- Intestinal and mesenteric lymph node lesions were collected and immediately preserved in 10% formal saline for histopathology. Semi thin tissue sections for histopathological examination was carried out according to the method described by Hoffman et al. ^[11].

 

Molecular detection and identification

DNA Extraction from tissues samples- DNA was extracted from intestine tissues (n=10) suspected samples using DNeasy^® Blood & Tissue Kit (Qiagen). Briefly, 25 mg from intestine tissues were taken and cut into small pieces, placed in a 1.5 ml microcentrifuge tube, 180 μl Buffer ATL and 20 μl proteinase K were added. The mixture vortexed incubated at 56°C until completely lysed and continuous the procedure according to the kit manufacturer’s protocol. The eluted DNA was stored at -20 C until used in PCR downstream reaction.

 Real time Quantitative PCR- A real-time qPCR assay was applied for detection of MAP bacteria, based on amplification of a 177bp fragment of MAP insertion element IS900 with set of specific primers and probe labeled with light cycler red 640 dye as described by Beumer et al. ^[12]; Rajeev et al.^[13]. In this assay, the Light cycler Fast Start DNA master hybprobe kit (Roche Diagnostics GmbH, Mannheim-Germany) and the light mix Mycobacterium Avium Paratuberculosis (MAP) kit (TIB MOLBIOL GmbH-Berlin-Germany) were used in an amplification reaction mixture. The mixture consisted of 2 µl 10x master mix, 2.4 µl 25 mM Mg²⁺, 2 µl of specific primers and probe sets solution and 5 µl DNA templates and completed to 20 µl with 8.4 µl PCR grade water. The PCR experiment was carried out in the Light Cycler 2.0 (Roche Diagnostics GmbH, Mannheim-Germany) with a protocol consisted of four thermal program steps: initial denaturation one cycle at 95°C for 10min, amplification in 50 cycles, each cycle segmented to 95°C for 5sec, 62°C for 5sec and 72°C for 15 sec, and finally melting in one cycle with 3 thermal steps (95°C for 20 sec, 40°C for 20sec and 85°C). The amplification crossing (CP) and melting (Tm) points were detected in 640 channels.

STATISTICAL ANALYSIS- The analysis was performed as described in light cycler instrument operator's manual, using the second derivative maximum method. The obtained data were analyzed with quantification analysis mode and the amplification signals were reported as crossing points (cycle's threshold) in channel 640. For further identification, the melting curve analysis mode was performed and specific melting points were detected by the same channel.

 

RESULTS

Clinical examination of investigated animals showed 10 (5 goats and 5 sheep) JD suspected animals out of 38 total examined. Suspected animals showed clinical signs included chronic weight loss, non-curable diarrhea, emaciation terminated by death. Gross pathology of suspected cases revealed thickening of the intestinal wall, corrugation and edematous of the mucosa and mesenteric lymph nodes hypertrophy and caseation (Fig. 1 and 2).  Other pathological lesions; muscular atrophy emaciation, fatty and mucoid degeneration, alopecia, edema, serous exudates in body cavities and anemia were seen. Histopathological examination of intestine tissues of suspected cases revealed cellular  infiltration  of epithelioid, lymphocyte, macrophage and giant cells and demonstration of free and phagocytosed acid fast bacilli  ( Fig. 3 and 4). The molecular examination of tissues from suspected animals  using real time polymerase chain reaction confirmed MAP infection in all 10 suspected  tissues samples (table 1) and (fig. 5 and 6). The resulted cycle thresholds (Ct) range from 14.5 to 32.72, with a mean of 25.587 and melting points (Tm) range from 68.41 to 68.85, with a mean of 68.53 and 0.339 standard deviations.

Fig. 1: Intestine of infected sheep shows corrugations, thickening and edematous of the mucosal wall

 

 

Fig. 2: Mesenteric lymph nodes of infected goat shows thickening, cording and edematous swelling 

 

 

Fig. 3: Semi thin section of mesenteric lymph node shows presence of coccobacilli organisms of MAP and infiltration of mononuclear cells, toluidine blue stain, 100X

 

Fig. 4: Semi thin section of intestine section shows presence of coccobacilli organisms of MAP and infiltration of mononuclear cells, toluidine blue stain, 100X

                                                                           

Table 1: Contains cycle’s threshold and melting point temperature of PAM tested by real time qPCR in light cycler 2.0 and analyzed with absolute and melting curve modes

* Ct- Cycle's threshold, **Tm- Melting point temperature

 

 

Fig. 5: displays the melting curves and melting temperatures points as analyzed by melting analysis mode in light cycler 2.0

 

 

Fig. 6: Displays the amplification curves and crossing points as analysed by absolute analysis mode in light cycler2.0

 

DISCUSSION- Johne's disease is serious economic and animal health consequences in domesticated ruminants (including sheep and goats) throughout the world ^[14,15]. In current study, Clinical examination of investigated small ruminant showed 10 (5 goats and 5 sheep) JD suspected animals out of 38 total examined. Suspected animals showed clinical signs included chronic weight loss, non-curable diarrhea, emaciation terminated by death. Clinical signs of JD in small ruminants are not specific and could be confused with other diseases as intestinal parasitism, chronic malnutrition, caseous lymphadenitis, ovine progressive pneumonia (OPP), environmental toxins, and cancer ^[16,17]. Gross pathology of suspected cases revealed thickening of the intestinal wall, corrugation and edematous of the mucosa and mesenteric lymph nodes hypertrophy and caseation.  These results came in line that obtained by Atif et al. ^[18]. Histopathological examination of intestine tissues of suspected cases revealed cellular infiltration of epithelioid, lymphocyte, macrophage and giant cells and demonstration of free and phagocytosed acid fast bacilli. These findings agreed with Clarke and Little ^[8]. Real time polymerase chain reaction confirmed MAP infection in all 10 suspected tissues samples. These results agreed with Green et al. ^[9] and Kawaji et al. ^[10]. This study confirmed the presence of MAP in tissues of suspected small ruminants when histopathological and RT-PCR methods were adopted.

 

CONCLUSIONS- Clinical screening of small ruminants for suspected cases of para tuberculosis confirmed by using histopathological and real-time polymerase chain reaction (RT-PCR) methods. Grossly, intestinal and mesenteric lymph nodes of suspected cases revealed thickening, corrugation and edematous swelling. Histopathologically, semi thin sections from the intestine and mesenteric lymph nodes stained with toluidine blue demonstrated MAP organism inside epithelium cells and macrophages. RT-PCR detected MAP IS900 gene in all suspected cases (100%) so we recommend using RT-PCR as a rapid sensitive method in diagnosis of PTB.

Based on the current study, early diagnosis among small ruminants is recommended for detection and control of the disease among sub-clinical animals, which could represent a source for dissemination of infection among other animals.

     

ACKNOWLEDGEMENT- The authors would like to thank Prof. Amel Omer Bakhiet, Prof. Gala Eldin Alazhri, Dr. Alhassan Mohamed, and Faculty of Veterinary Medicine, Sudan University of Science and Technology for support.  

 

CONTRIBUTION OF AUTHORS- MI and GA planned the study. MI and EM designed and performed the work. GA and AO guided the research throughout the study. Both authors wrote and revised the paper and approved the submission of the manuscript.

MI= Mohamed Alamin Ibrahim Hamid, GA= Galal Eldin Elazhari Mohammed, AO= Amel Omer Bakhiet, EM= Elhassan Mohamed Ali Saeed.

 

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